bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal mechanisms of human alpha‐atrial natriuretic peptide in man.
Authors: Brown J , Corr L
Published: December 2014

1. Eight normal volunteers were studied on two separate days after being dehydrated overnight. Each volunteer received a background intravenous infusion of arginine vasopressin (5.5 X 10(‐7) i.u. kg‐1 min‐1) on both days and also received an intravenous infusion of human alpha‐atrial natriuretic peptide (15 pmol kg‐1 min‐1) plus carrier on one day and carrier alone on the other. The ensuing changes in blood pressure, in the excretion of urinary solutes, and in the excretion of solute‐free water were recorded. 2. The infusion of atrial peptide had a small hypotensive effect, and increased the rate of excretion of sodium but not of potassium. There were no significant changes of urinary osmolality or of creatinine clearance. 3. The infusion of atrial peptide increased the rate of solute‐free water reabsorption and did so in direct proportion to its effect of increasing sodium excretion. 4. A further six normal, dehydrated volunteers were studied on each of two days after taking 500 mg of lithium carbonate on the previous evening. On one day, they received an intravenous infusion of human alpha‐atrial natriuretic peptide (15 pmol kg‐1 min‐1) plus carrier and on the other day they received carrier alone. The excretion of urinary electrolytes and the creatinine clearance were recorded. 5. The infusion of atrial peptide produced significant increases in the rates of excretion of both sodium and lithium, but there were no such changes of creatinine clearance. 6. Another six normal volunteers were studied on each of two days. On each day they drank 2 l of water over 30 min and then water to replace their urinary losses. They also received loading doses and maintenance infusions of inulin and sodium para‐aminohippurate. Once a full water diuresis had become established, each subject received an infusion of human alpha‐atrial natriuretic peptide (15 pmol kg‐1 min‐1) plus carrier on one day and carrier alone on the other, exactly as before. The excretion of sodium and solute‐free water, and the clearances of inulin and para‐amino‐hippurate were recorded. 7. The infusion of atrial peptide increased the rates of excretion of both sodium and solute‐free water. It also increased the clearance of inulin, but not that of para‐aminohippurate. 8. These results suggest that, in our volunteers, infusion of human alpha‐atrial natriuretic peptide increases sodium excretion mainly by increasing the delivery of sodium along the renal tubule from sites upstream of the loop of Henle.(ABSTRACT TRUNCATED AT 400 WORDS)
The dynamic response of cat gastrocnemius motor units investigated by ramp‐current injection into their motoneurones.
Authors: Baldissera F , Campadelli P , Piccinelli L
Published: December 2014

1. The isometric force developed by single motor units in response to injection of ramp‐and‐hold currents into their motoneurones was recorded from the common tendon of the gastrocnemius muscles of the cat. The average rate of rise of the force (force‐slope) produced by the ramp‐evoked discharge, was found to grow almost linearly with the rate of current injection (current‐slope) up to a saturation value (maximal force‐slope). 2. The slope of the function which links the force slope to the current‐slope is the gain (dF/dI) of the motor unit under dynamic conditions. The value of the dynamic gain, measured in the linear region of growth, displays a large variability, i.e. for each nanoampere of current injected, the force developed is as much as 40 times larger in the strongest than in the weakest motor units. Such large gain differences, however, are drastically reduced if the force is expressed as a percentage of the maximal tetanic tension, Ft: per nanoampere injected, most of the units deliver from 1.0 to 3.0% of Ft. 3. The maximal force‐slope which each unit could reach exhibits a large variability, ranging from 0.06 to 4.0 g ms‐1. Like the dynamic gain, the maximal force‐slope is positively related to Ft. 4. It was found that the dynamic sensitivity of the motoneurone, i.e. the increase of the firing rate per unitary increase of the current‐slope, governs the fractional growth of the force‐slope, whereas the motor unit contraction time determines the firing rate at which maximal force‐slope is reached. Together, the two factors co‐operate in defining, for each motor unit, the range of input‐slopes within which the force‐slope is regulated. 5. The motoneurones which supply the weak motor units, those with the lowest dynamic gain, have higher dynamic sensitivity and lower rheobase than those innervating the strong motor units. This suggests that weak motor units need less synaptic current both to be recruited and to reach the maximal speed of force development when their input is supraliminal.
Transmural coronary vasodilator reserve and flow distribution during maximal exercise in normal and splenectomized ponies.
Authors: Manohar M
Published: December 2014

1. Transmural distribution of myocardial blood flow was studied using 15 micron diameter radionuclide‐labelled microspheres in six normal ponies and nine splenectomized ponies at rest, and during maximal exercise performed without as well as with adenosine infusion (3 microM kg‐1 min‐1). The splenectomized ponies were also studied during submaximal exercise performed at 75% of the workload. 2. Maximal exertion in normal ponies increased heart rate (348%), mean arterial blood pressure (40.9%), rate‐pressure product (563%), arterial O2 content (43.2%), and mean pulmonary artery pressure (247%). Accompanying these changes, the left ventricular, septal and right ventricular myocardial blood flows increased 419, 500, and 921% above control values, respectively, and the perfusion in all regions became nearly homogeneous. 3. Adenosine infusion during maximal exercise in normal ponies caused further significant increments in transmural myocardial blood flow in all regions as coronary vascular resistance decreased, thereby demonstrating considerable unutilized coronary vasodilator capacity. 4. In splenectomized ponies, with maximal exercise heart rate rose to a similar value as in normal ponies but mean aortic pressure, rate pressure product, pulmonary artery pressure and arterial O2 content were significantly less than in normal ponies (P less than 0.01). 5. Transmural myocardial perfusion in the splenectomized ponies also increased markedly with both exercise intensities and no significant differences were observed. 6. In the left ventricle and the septum of splenectomized ponies, transmural blood flow levels during maximal exertion were significantly higher (P less than 0.05) than in normal ponies. Adenosine infusion during maximal exercise in splenectomized ponies failed to cause further increments in blood flow to the inner layers of the left ventricle and the septum. 7. It is concluded that marked augmentation of arterial O2 content in normal ponies helped limit the increment in left ventricular myocardial perfusion required during maximal exertion, and thereby helped preservation of considerable unutilized coronary vasodilator capacity.
Gating properties of the mechano‐electrical transducer channel in the dissociated vestibular hair cell of the chick.
Authors: Ohmori H
Published: December 2014

1. The gating property of a mechano‐electrical transduction (m‐e.t.) was studied in dissociated chick vestibular hair cells having hair bundles of varying length (from 7 to more than 30 microns long). The whole‐cell recording voltage‐clamp technique was used to record m‐e.t. currents, and mechanical stimuli were applied to the hair bundle with a rigid glass rod. 2. Displacements of the glass rod and the hair bundle were measured with a resolution of 0.1 micron from contrast‐enhanced television images. The motion of the hair bundle was tightly coupled to the motion of the stimulating glass rod, and displacements were not detected in the circumference of the cell body. Thus, all the displacement applied to the hair bundle resulted in bending about the insertion into the cuticle and relative to the cell body. 3. Displacements of the hair bundle towards the taller stereocilia generated inward‐going m‐e.t. currents at negative membrane potentials, while displacements of the hair bundle towards the shorter stereocilia generated outward‐going m‐e.t. currents. These outward going m‐e.t. currents reflect closing of the m‐e.t. channels which are open at the resting position of the hair bundle. The fraction of these channels open at the resting position was 0.12 +/‐ 0.04 (n = 7). 4. The displacement‐response relationship measured both at ‐50 mV and at +38 mV were superimposable after scaling. Thus, no voltage dependence was observed in gating of the m‐e.t. conductance. 5. When a hair bundle of a shorter length (less than 7.5 microns long) was stimulated at 5 micron form the insertion to the cuticle, the minimum hair‐bundle displacement which could generate a detectable amount of m‐e.t. current was 0.01 micron. The transduction current was linearly related to the hair‐bundle displacement for values of up to 0.6 micron towards the taller stereocilia, and showed saturation with larger displacements. 6. When a hair bundle of a longer length (more than 12.5 microns long) was stimulated (towards the taller stereocilia) at 10 micron from the insertion to the cuticle the m‐e.t. current generated was linear for displacements of up to 1.5 micron, and saturated with larger displacements. 7. The above two points suggest that the range of linear transduction becomes wider as the length of the hair bundle becomes longer under in situ conditions where the displacement is likely to be applied at the tip of the hair bundle.(ABSTRACT TRUNCATED AT 400 WORDS)
Responses of Purkinje cells and mossy fibres in the flocculus of the monkey during sinusoidal movements of a visual pattern.
Authors: Noda H , Warabi T
Published: December 2014

1. Discharges of Purkinje cells (P cells) and mossy fibres were recorded from the cerebellar flocculus of monkeys trained to fixate a stationary visual target. The units were tested with a sinusoidally moving random dot pattern (background) which was projected on an entire screen or on part of it. The receptive field organization of the units was tested by changing the area of stimulus presentation on the screen and by changing the direction of visual fixation. 2. When stimulated with sinusoidal movements of the background in the horizontal plane, ninety‐two of 684 Purkinje cells (13.5%) responded to the retinal‐slip velocity. Seventy‐eight of the ninety‐two visually responsive Purkinje cells (84.8%) also showed cyclic modulations in activity during horizontal smooth‐pursuit eye movements (these were so‐called horizontal gaze‐velocity Purkinje cells). 3. In response to the sinusoidal retinal‐slip velocity, the visual Purkinje cells showed six types of discharge patterns. Type 1 Purkinje cells (28/92 or 30.4%) were directionally selective: they showed a peak activity during background movement in one direction and a trough in the other. Both peaks and troughs were related to stimulus velocities. Their receptive fields were relatively large (greater than 45 deg) and included the fovea. 4. Type 2 (8/92 or 8.7%) and type 3 (5/92 or 5.4%) Purkinje cells showed sinusoidal responses similar to those of type 1 Purkinje cells, but the visual inputs were primarily excitatory in type 2 Purkinje cells and inhibitory in type 3 Purkinje cells. Only the peaks in type 2 and troughs in type 3 were related to stimulus velocities. 5. Type 4 (4/92 or 4.3%) and type 5 (11/92 or 12.0%) Purkinje cells showed responses to stimulus movements in both directions (bidirectional). When the moving background was projected with 10 deg of fixation, type 4 Purkinje cells were excited bidirectionally in relation to retinal‐slip velocities. When the periphery of either hemiretina was stimulated, type 5 Purkinje cells were inhibited and the trough activity was stimulus‐velocity dependent. Receptive fields were found in the ipsilateral hemiretinae in seven type 5 Purkinje cells and in the contralateral hemiretinae in the remaining four type 5 Purkinje cells. 6. Type 6 (36/92 or 39.1% Purkinje cells received an excitatory input from the central retina and an inhibitory input from the periphery. The peripheral receptive fields were either in the ipsilateral (69.4%) or contralateral (30.6%) hemiretinae of both eyes.(ABSTRACT TRUNCATED AT 400 WORDS)
Mapping calcium transients in the dendrites of Purkinje cells from the guinea‐pig cerebellum in vitro.
Authors: Ross W N , Werman R
Published: December 2014

1. A 10 X 10 photodiode array was used to detect stimulation‐dependent absorbance changes simultaneously from many positions in the dendrite field of guinea‐pig Purkinje cells which had been injected with the calcium indicator Arsenazo III in thin cerebellar slices. Signals from each element of the array were matched to positions on the cells by mapping them onto fluorescence photographs of Lucifer Yellow which had been co‐injected into the cells with the Arsenazo III. 2. In response to intrasomatic stimulation the rising phase of the absorbance signals corresponded in time with the calcium spikes recorded with an intracellular electrode. There was no increase in absorbance during bursts of fast sodium spikes. Absorbance signals persisted after the sodium spikes were blocked by tetrodotoxin (TTX). In addition, the signals were largest at 660 nm and small signals of opposite polarity were found at 540 nm. These results indicate that the absorbance signals came from calcium entry into the cell resulting from the turning on of voltage‐dependent calcium conductances. 3. In these experiments signals were usually seen all over the dendritic field and were weak or totally absent over the soma. In some cases signals were seen over a more restricted area. With a spatial resolution of 25 microns we were not able to see any evidence for highly localized sites of calcium entry. 4. Sometimes the rising phase of the calcium signals was separated by almost 13 ms in different parts of the dendritic field, too long to be explained by active propagation delay. This suggests that calcium spikes causing these signals can be evoked separately in different regions of the Purkinje cell dendritic field by long‐lasting potentials which may reach local threshold at different times. 5. Calcium signals resulting from slow plateau after‐potentials and the calcium spikes produced by them were also detected in all locations in the dendritic field. The relative distribution of amplitudes from these plateau signals was different from the distribution of evoked signals during current injection. 6. Climbing fibre synaptic activation produced calcium signals which were distributed over the dendritic arborization, but larger at the main dendritic tree where most of the synaptic contacts are located. 7. Calcium signals were also detected from the dendrites of other neurone types in the in vitro slice preparation. Thus, it is likely that these kind of measurements can be used to analyse the electroresponsiveness of many kinds of neurones in the mammalian brain.
Morphological and physiological studies of development of the monosynaptic reflex pathway in the rat lumbar spinal cord.
Authors: Kudo N , Yamada T
Published: December 2014

1. The developmental process of the monosynaptic reflex pathway was investigated morphologically and electrophysiologically in isolated lumbar spinal cords of new‐born and fetal rats. 2. Dorsal root fibres were stained with horseradish peroxidase in the fourth lumbar (L4) segment at different ages ranging from embryonic day (E) 15.5 to post‐natal day (P) 0. At E15.5, several collaterals issued from axons in the dorsal funiculus and reached the dorsal part of the dorsal horn. At E16.5, the number of collaterals entering the grey matter increased. Also, a group of collaterals extended ventralwards forming a bundle, and reached the intermediate region. At E17.5, a small number of collaterals reached the motor nuclei. The number of collaterals entering the motor nuclei increased almost linearly with age: 0 at E15.5 and at E16.5, 27 at E17.5, 184 at E18.5, 432 at E19.5 and 746 at P0. 3. The tips of collaterals and their branches had growth cones, boutons (round or oval varicosities) or other varicosities. The mean number of branches with these structures per collateral in the motor nuclei was 1.2 at E17.5, 2.5 at E18.5, 3.6 at E19.5 and 5.8 at E20.5. 4. The percentage of collaterals having growth cones in the motor nuclei was 75% at E17.5, 70% at E18.5, 38% at E19.5 and 15% at E20.5. 5. The mean number of boutons per collateral in the motor nuclei was 0.6 at E17.5, 3.2 at E18.5, 4.9 at E19.5 and 10.7 at E20.5. This increase with age was caused by both branching of collaterals and the increase in the number of boutons of the en passant type. The estimated total number of boutons in the motor nuclei of the L4 segment steeply increased after E17.5: 16 at E17.5, ca. 600 at E18.5, ca. 2000 at E19.5 and ca. 8000 at E20.5‐P0. 6. Stimulation of the L4 dorsal root evoked a reflex response in the L4 ventral root, recorded as the ventral root potential, in two out of nine preparations at E15.5 and in all preparations at and after E16.5. The onset of the ventral root potential indicated the onset of excitatory post‐synaptic potentials in motoneurones. The segmental latency of the ventral root potentials was markedly shortened between E17.5 and E18.5 (from 12.5 to 7.2 ms) and essentially unchanged at the later stages. 7. The magnitude of monosynaptic reflex responses in the L4 segment gradually increased with age during prenatal stages, becoming maximal at P2‐3 and then decreased at the following stages (P4‐P8).(ABSTRACT TRUNCATED AT 400 WORDS)
Electrophysiological and dye‐coupling studies on secretory, myoepithelial and duct cells in human eccrine sweat glands.
Authors: Jones C J , Kealey T
Published: December 2014

1. Electrophysiological properties and dye‐coupling status of secretory, myoepithelial and coiled duct cells in isolated human eccrine sweat glands have been assessed by single‐micro‐electrode studies and intracellular micro‐iontophoresis of the fluorescent naphthalimide dye Lucifer Yellow CH (molecular weight 457). Treated glands were embedded in LKB HistoResin and examined by transmission fluorescence microscopy, first as wholemounts and then as 5 microns serial sections. Sections positive for Lucifer Yellow were photographed and then stained with Toluidine Blue for observation by conventional microscopy to confirm the site of penetration. 2. Out of forty‐five successful micro‐iontophoreses, three were confirmed in secretory cells, twelve in myoepithelial cells and thirty in cells of the coiled duct wall. The latter were identified as the most penetrable in the coiled part of the isolated human eccrine sweat gland. 3. Of the three secretory cells labelled (resting potentials ‐40, ‐52 and ‐63 mV), all demonstrated dye coupling to neighbouring secretory cells although in one case this was found to be selective. Not every secretory cell was involved in coupling. No fluorescent label spread to the myoepithelial cells which form a network on the basal surface of the secretory tubule. 4. When myoepithelial cells were penetrated, they demonstrated dye coupling to neighbouring myoepithelial cells but not to secretory cells with which they also made contact. Basal resting potentials of ‐35 to ‐65 mV were recorded (mean = ‐52 mV, S.E. of mean = +/‐ 2.4 mV, n = 12) and, in eight out of the twelve cells penetrated and labelled, spontaneous depolarizing transients were also observed whose amplitude but not frequency increased with increasing membrane polarization. Administration of acetylcholine to produce a final concentration of 10(‐6) to 10(‐7) M produced either depolarization or micro‐electrode dislodgement. 5. Of the thirty cells labelled in the coiled duct, twenty‐six showed obvious dye spread to neighbouring cells in both layers of the wall. There was no relation between dye‐coupling status and basal resting potential which lay in the range ‐40 to ‐82 mV (mean = ‐60 mV, S.E. of mean = +/‐ 2.4 mV, n = 30). Repeated doses of acetylcholine produced either no response from cells in this range or depolarization in cells with resting potentials more negative than ‐70 mV and hyperpolarization in cells with resting potentials more positive than ‐70 mV. In addition, there was a biphasic response, depolarization followed by hyperpolarization in a cell of resting potential ‐67 mV.(ABSTRACT TRUNCATED AT 400 WORDS)
Cardiovascular and phrenic nerve responses to stimulation of the amygdala central nucleus in the anaesthetized rabbit.
Authors: Cox G E , Jordan D , Paton J F , Spyer K M , Wood L M
Published: December 2014

1. The cardiovascular responses to electrical stimulation of the central nucleus of the amygdala (c.n.) have been studied in chloralose‐anaesthetized rabbits. A pattern of response involving bradycardia, hypotension and hind‐limb vasodilatation, accompanied by an increase in the rate of phrenic nerve discharge, was evoked only in response to stimulation within the medial portion of the c.n. 2. The cardiovascular responses were not secondary to the changes in respiratory activity since they were unaffected by altering central respiratory drive by either hypo‐ or hyperventilation of the animal. 3. The bradycardia was attenuated by the administration of atropine sulphate and abolished by the subsequent administration of propranolol, which when given alone attenuated the bradycardia. Atropine or propranolol given alone also attenuated the hypotension evoked by medial c.n. stimulation but the concurrent hind‐limb vasodilatation was unaffected. 4. Atenolol, which unlike propranolol does not cross the blood‐brain barrier, had little effect on the bradycardia in response to medial c.n. stimulation, but the subsequent administration of atropine abolished it. The hypotension in response to medial c.n. stimulation was also unaffected by atenolol. 5. The vasodilatation in response to medial c.n. stimulation was abolished by administration of guanethidine even after restoration of hind‐limb perfusion pressure to control values by the infusion of angiotensin II into the hind‐limb perfusion circuit. 6. Electrical stimulation of areas within 0.5 mm of the medial c.n. also resulted in bradycardia but then it was accompanied by hypertension and hind‐limb vasoconstriction. Stimulation of areas 1.0 mm distant to the medial c.n. resulted in small and inconsistent cardiovascular responses. 7. These results show that hind‐limb vasodilatation, mediated by withdrawal of sympathetic tone, occurs in response to stimulation within the medial c.n. of the rabbit and is in part responsible for the observed hypotension. It has also been confirmed that the bradycardia in response to medial c.n. stimulation is mediated by the vagus nerves.
Sodium currents in dissociated bull‐frog sympathetic neurones.
Authors: Jones S W
Published: December 2014

1. Sodium currents were recorded from the cell bodies of single dissociated sympathetic neurones of bull‐frogs, using patch electrodes in the whole‐cell configuration, in Cs+‐loaded cells, using external Mn2+ to block calcium currents. 2. A discontinuous single‐electrode voltage‐clamp method was used. Switching frequencies of 40‐50 kHz were possible with 0.5‐2 M omega electrodes, giving clamp settling times of approximately 0.2 ms and adequate clamp of currents up to 30 nA. 3. The sodium currents required unusually positive voltages for both activation and inactivation, with half of the maximal observed conductance activating at +2 mV, and half‐maximal steady‐state inactivation at ‐35 mV. Both fast (in the order of milliseconds) and slow (in the order of seconds) inactivation processes occurred. 4. Two pharmacologically and kinetically distinct sodium currents were observed. The larger current was blocked by tetrodotoxin (TTX) and saxitoxin (STX) with I50 values (i.e. the concentration which results in 50% inhibition) of 10 nM or lower, and activated and inactivated relatively rapidly. 5. A smaller current (approximately 25% of peak current) was blocked by 0.1‐1 microM‐STX but not by 1‐10 microM‐TTX. It also activated rapidly, but inactivated approximately 3‐fold more slowly than the larger current. The slower current was blocked 75‐90% by Cd2+ (50‐200 microM).
Effects of atrial natriuretic polypeptide on rat hypothalamic neurones in vitro.
Authors: Okuya S , Yamashita H
Published: December 2014

1. Extracellular recordings were made from 175 spontaneously active cells in the rat coronal hypothalamic slice preparation. Reconstruction of the recording sites showed that fifteen were in the supraoptic nucleus (s.o.n.), ten in the magnocellular portion of the paraventricular nucleus (p.v.n.) which could be antidromically activated by stimulation lateral to the nucleus, seventy‐seven other cells in the p.v.n. and seventy‐three in the anteroventral third ventricle (a.v.3.v.) region. 2. The mean firing rates (mean +/‐ S.E. of mean) of the spontaneously firing cells in the s.o.n., p.v.n. and a.v.3.v. were 2.8 +/‐ 0.4 spikes/s, 2.9 +/‐ 0.2 spikes/s and 5.0 +/‐ 0.4 spikes/s, respectively. Antidromically identified p.v.n. cells fired spontaneously with a mean firing rate of 1.5 +/‐ 0.5 spikes/s. 3. Bath application of atrial natriuretic polypeptide (a.n.p.; 10(‐7) M) had no effect on fifteen s.o.n. cells tested but nineteen (22%) of eighty‐seven p.v.n. cells (including two of the ten antidromically activated cells) and thirty (41%) of seventy‐three a.v.3.v. cells showed inhibitory responses. Three (3%) cells in the p.v.n. were excited by a.n.p. 4. The dose dependence of the response to a.n.p. was tested in two p.v.n. and five a.v.3.v. cells. As a.n.p. concentration increased, the firing rates of all seven cells generally decreased. However, one a.v.3.v. neurone was excited at low concentrations (less than 10(‐8) M) but inhibited at high concentrations (10(‐7) and 10(‐6) M) of a.n.p. The threshold concentration to evoke inhibitory responses in the p.v.n. was 10(‐10) M and in the a.v.3.v. was 10(‐11) M. 5. With the exception of the two antidromically activated p.v.n. cells, the inhibitory effect of a.n.p. still persisted after synaptic transmission had been suppressed with a low‐Ca2+ and high‐Mg2+ medium. 6. Thirty‐six cells in the a.v.3.v. were tested with both a.n.p. and angiotensin II applied at 10(‐7) M. Twelve showed inhibitory responses to a.n.p. and nine showed excitatory responses to angiotensin II. In other experiments, a.n.p., angiotensin II and arginine‐vasopressin were each applied to neurones in the p.v.n. Of the forty cells tested with all three peptides at 10(‐7) M, seven were inhibited by a.n.p., fourteen were excited by angiotensin II and twenty were excited by arginine‐vasopressin. No neurones in either the p.v.n. or a.v.3.v. were inhibited by a.n.p. and excited by angiotensin II, but four neurones in the p.v.n. were inhibited by a.n.p. and excited by arginine‐vasopressin.(ABSTRACT TRUNCATED AT 400 WORDS)
Membrane properties of morphologically identified X and Y cells in the lateral geniculate nucleus of the cat in vitro.
Authors: Crunelli V , Leresche N , Parnavelas J G
Published: December 2014

1. The membrane properties and the electrotonic features of cells in lamina A of the cat dorsal lateral geniculate nucleus (l.g.n.) were studied using an in vitro slice preparation. 2. Following intrasomatic injection of horseradish peroxidase (HRP) each neurone was classified as an X (n = 20) or a Y (n = 27) cell on the basis of its morphology. For both classes, the frequency distribution of soma area was similar to that reported in vivo where the identification of X and Y cells in lamina A of the cat l.g.n. was based on physiological criteria. 3. No difference was observed in the mean resting membrane potential between the two classes of cells. However, the input resistance (RN) of X cells was greater (82 M omega) and their membrane time constant (tau 0) longer (22 ms) than of Y cells (RN, 32 M omega; tau 0, 15 ms). 4. Using a simple neuronal model, the calculated electrotonic length (L) and the dendritic to somatic conductance ratio (rho) were similar for the two classes of cells. The mean value of L (0.7) and rho (1.9) suggests that both X and Y cells are electrically compact. 5. The specific membrane resistance (Rm, 28,000 omega cm2) of X cells, calculated using two different approaches, was found to be higher than that of Y cells (17,000 omega cm2). 6. The implication of these results for the integration of synaptic signals in the two classes of l.g.n. cells and the feasibility of differentiating between X and Y cells on the basis of their membrane properties are discussed.
The effect of myasthenic syndrome antibody on presynaptic calcium channels in the mouse.
Authors: Lang B , Newsom-Davis J , Peers C , Prior C , Wray D W
Published: December 2014

1. The action of immunoglobulin G obtained from patients with Lambert‐Eaton myasthenic syndrome (LEMS IgG) was investigated by injecting mice, followed by intracellular recordings from the mouse diaphragm. 2. End‐plate potential quantal content was studied over a range of Ca2+ concentrations. Curves of log quantal content versus log Ca2+ concentration were shifted to the right by LEMS IgG. For low Ca2+ concentrations, release continued to follow Poisson statistics after LEMS IgG treatment. 3. Miniature end‐plate potential (m.e.p.p.) frequency was measured in solutions containing high K+ concentrations. LEMS IgG significantly reduced m.e.p.p. frequency at each K+ concentration studied. 4. M.e.p.p. frequency was measured at fixed high‐K+ concentration (15.9 mM) for a range of Ca2+ concentrations. The log‐log plot of m.e.p.p. frequency versus Ca2+ concentration was shifted downwards throughout by LEMS IgG. 5. M.e.p.p. frequency was not affected by LEMS IgG in Ca2+‐free solutions (K+ concentration 15.9 mM) or in solutions of low Ca2+ concentration (K+ concentration 5.9 mM). 6. At each Ca2+ concentration studied, m.e.p.p. amplitudes were not affected by LEMS IgG. 7. The data suggest that LEMS IgG acts on presynaptic voltage‐dependent Ca2+ channels to cause their loss of function, probably by down‐regulation.
The properties and function of inward rectification in rod photoreceptors of the tiger salamander.
Authors: Hestrin S
Published: December 2014

1. Rod photoreceptors were isolated from the retinae of tiger salamanders and voltage clamped using the whole‐cell patch‐clamp technique. 2. Hyperpolarizing the cell to potentials more negative than ‐50 mV evoked an inward current termed Ih. 3. Ih did not turn on immediately following a hyperpolarizing step but showed a marked delay. The activation time course of Ih could be described by the sum of two exponential components of opposite polarity. 4. The steady‐state chord‐conductance was half activated at ‐67 mV. 5. The reversal potential of Ih was close to ‐30 mV in normal standard salt solution. Increasing the external potassium concentration tenfold shifted the reversal potential by +17 mV. 6. The conductance‐voltage relation and the kinetic parameters were not affected by changes in the external potassium concentration. 7. When fully activated, the zero‐current conductance underlying Ih depended on the square root of the concentration of external potassium. 8. The permeability ratio PNa/PK depended on the external potassium concentration. It was 0.2 at an external potassium concentration of 2.0 mM and 0.3 at an external potassium concentration of 10.0 mM. The interaction of potassium with Ih suggests that Ih is a multi‐ion pore. 9. It is concluded that Ih differs from the inward rectifier that is found in egg cells, frog muscle and heart muscle. 10. The kinetics and voltage sensitivity of Ih suggest that it does not play a role in the dark resting state or in the response to dim flashes of light. Its properties indicate that it may have a major role in the response to bright flashes.
Effects of central or peripheral axotomy on membrane properties of sensory neurones in the petrosal ganglion of the cat.
Authors: Gallego R , Ivorra I , Morales A
Published: December 2014

1. The properties of sensory neurones in the petrosal ganglion of the cat were examined in vitro with intracellular electrodes 8 days after section of the central (bulbar roots) or peripheral process. Two types of cells, both with conduction velocities faster than 2 m/s and with humps on the falling phases of their action potentials (H‐neurones), were studied: glossopharyngeal neurones arising from the tongue and pharynx, and carotid neurones originating in the carotid body and carotid sinus. 2. Peripheral axotomy produced an increase in action potential duration and a marked decrease in the amplitude and duration of the spike after‐hyperpolarization in both glossopharyngeal and carotid neurones. 3. The maximum rate of depolarization of the action potential increased after peripheral axotomy in glossopharyngeal cells but did not change in carotid neurones. 4. The time‐dependent inward rectification in response to hyperpolarizing pulses was markedly reduced in both types of cells after peripheral axotomy. 5. Section of the peripheral process produced a decrease of the rheobase of glossopharyngeal cells, but not of carotid neurones. After axotomy the proportion of cells giving tonic discharges in response to long depolarizing pulses increased from 13 to 54% among carotid neurones but did not change in glossopharyngeal cells. 6. No significant changes in membrane potential or input resistance of either group of cells were found after peripheral axotomy. 7. Central axotomy did not produce any changes in the electrophysiological properties of glossopharyngeal or carotid neurones. 8. Peripheral conduction velocity was decreased in both types of cells after peripheral axotomy, but did not change after section of the bulbar roots. 9. It is concluded that the electrical properties of sensory neurones are modified after peripheral axotomy but not after central axotomy. Furthermore, the changes produced by peripheral axotomy are different in neurones innervating different peripheral targets. 10. The possibility that some electrical properties of sensory neurones are maintained by their peripheral targets is discussed.
The contribution of intracellular acidosis to the decline of developed pressure in ferret hearts exposed to cyanide.
Authors: Eisner D A , Elliott A C , Smith G L
Published: December 2014

1. The concentrations of phosphorus‐containing metabolites were measured using 31P nuclear magnetic resonance (n.m.r.) in Langendorff‐perfused ferret hearts. The hearts were stimulated at a constant rate and developed pressure was measured. 2. The inhibition of oxidative phosphorylation with cyanide (2 mM) decreased developed pressure. This was accompanied by an intracellular acidosis, a fall in the concentration of phosphocreatine ([PCr]) and a rise in that of inorganic phosphate ([Pi]). 3. The effects of cyanide on developed pressure were compared with those of simply decreasing the intracellular pH (pHi) (by elevating CO2) to match the change produced by cyanide. The change of pHi alone resulted in about 33% of the decrease of force produced by cyanide. 4. The relationship between developed pressure and pHi was investigated by altering CO2. It could be described by an equation of the form:log developed pressure = a + b pHi where a and b were independent of pHi. The addition of cyanide decreased a but had no significant effect on b. In other words a given change of pHi had the same fractional effect on pressure in the absence as in the presence of cyanide. 5. In another series of experiments, after cyanide had been added, pHi was returned to control levels by decreasing CO2. This increased developed pressure. Nevertheless the pressure was still considerably less than in control. Furthermore, if the acidosis was abolished by decreasing CO2 at the same time as cyanide was added developed pressure still decreased. 6. We conclude that most of the decrease of developed pressure produced by cyanide is not produced by intracellular acidosis and may result from increased [Pi].
Neural activity in the regenerating optic nerve of the goldfish.
Authors: Northmore D P
Published: December 2014

1. Retinal ganglion cells of one eye were axotomized in goldfish either by sectioning the contralateral optic tract or by ablating the contralateral lobe of the optic tectum. Between 2 and 40 days later, multiunit activity in response to diffuse light flashes was recorded from the axotomized and normal optic nerves, and from the optic tectum. 2. Two days after tract section, the amplitude of the integrated multiunit response of the axotomized nerve was normal. By 16 days it had fallen to 15% of control values, at which time visual responses carried by the regenerating tract were first recorded in tectum. Activity in the axotomized nerve then recovered gradually. 3. After ablation of one tectal lobe, multiunit responses in the axotomized nerve had not recovered by 40 days. 4. Integrated spontaneous activity in the axotomized nerve was depressed with a similar time course to the depression of light‐evoked activity, both after tract section and tectal ablation. 5. Retinal ganglion cell nuclear size, a morphological indicator of the cell body reaction, varied inversely with evoked activity, whether axotomy was by tract section or by tectal ablation. 6. Electrically evoked compound action potentials of normal amplitude could be recorded from an axotomized nerve despite depressed responses to light flashes. 7. It is concluded that optic nerve axotomy in goldfish reduces the number of optic fibres carrying impulses and/or the frequency of their discharge. The effect is closely linked to morphological changes occurring in the retinal ganglion cell bodies. Recovery of impulse activity and morphology depends upon the regenerating optic fibres innervating an appropriate target.
Renal haemodynamic actions of pressor doses of lysine vasopressin in the rat.
Authors: Lote C J , McVicar A J , Thewles A
Published: December 2014

1. Dose‐response effects of lysine vasopressin on renal haemodynamics were studied in conscious rats infused with 2.5% (w/v) dextrose solution at 5.8 ml/h. 2. Lysine vasopressin was maximally antidiuretic in the absence of a significant pressor effect at a dose of 2.5 pmol h‐1 100 g body weight‐1. Doses of vasopressin greater than this induced a dose‐dependent increase in arterial blood pressure. 3. The clearance of p‐aminohippurate (PAH) was not significantly changed by vasopressin, even at pressor doses. Rats pre‐treated with indomethacin to inhibit prostaglandin synthesis showed a decrease in PAH clearance during the infusion of vasopressin at a dose of 30 pmol h‐1 100 g body weight‐1, and this suggests that the renal vasoconstrictor actions of vasopressin are attenuated by dilator prostaglandins. 4. Inulin clearance was unchanged by non‐pressor doses of vasopressin but was decreased in a dose‐dependent manner by pressor doses. A maximal effect was induced by a dose of 30 pmol h‐1 100 g body weight‐1 which decreased inulin clearance from 3.23 +/‐ 0.76 (mean +/‐ S.E. of mean) to 1.60 +/‐ 0.37 ml/min (P less than 0.02). A change in inulin clearance (from 3.42 +/‐ 0.46 to 2.17 +/‐ 0.33 ml/min, P less than 0.01) was also observed in rats pre‐treated with indomethacin and infused with vasopressin at the same dose. The magnitude of the change was not significantly different from that observed in rats which were not treated with indomethacin. 5. Control rats infused with dextrose showed a slight but significant increase in sodium excretion during the course of the experiment. A similar natriuresis was observed in rats infused with non‐pressor doses of vasopressin but was considerably enhanced in rats infused with pressor doses of the peptide. The antidiuresis induced by vasopressin remained maximal in rats infused with pressor doses. 6. Potassium and osmolal outputs were unchanged by non‐pressor doses of vasopressin but significantly increased during administration of pressor doses. 7. It is concluded that pressor doses of lysine vasopressin do not alter total renal perfusion in conscious rats when the prostaglandin system is intact. Glomerular filtration is, however, decreased in a dose‐dependent manner by these amounts but the mechanism is unclear.
A patch‐clamp study of mammalian platelets and their voltage‐gated potassium current.
Authors: Maruyama Y
Published: December 2014

1. Mammalian platelets were freshly isolated from human, rabbit, or rat blood. The whole‐cell and cell‐attached voltage‐clamp variations of the patch‐clamp technique were employed to study the passive electrical properties and ion channels of unstimulated platelets. 2. The input capacitance of a platelet measured by the phase‐sensitive detection method was about 128 fF, the input resistance of a platelet was about 59 G omega and the resting membrane potential was about ‐50 mV which was directly measured by a whole‐cell recording in the current‐clamp mode. 3. The predominant ion channel was a voltage‐gated K+ channel resembling the delayed rectifier K+ channel of nerve, muscle and T‐lymphocyte. There was no indication of any inward current in the platelet membrane. The activation of the K+ current could be fitted by n4 kinetics, and was half‐maximal at about ‐35 mV. 4. The time constant of K+ current inactivation was virtually independent of voltage and varied from cell to cell. Recovery from inactivation was slow and dependent on the size and duration of the preceding conditional voltage step. Steady‐state inactivation was half‐maximal at about ‐50 mV and was complete at positive potentials. 5. The predominant single‐K+‐channel conductance was 9 pS and the estimated number of K+ channels per platelet was about 325, corresponding to a density of 25/micron2 apparent membrane area.
Sensory fibres modulate histamine‐induced catecholamine secretion from the rat adrenal medulla and sympathetic nerves.
Authors: Khalil Z , Livett B G , Marley P D
Published: December 2014

1. We have studied the mechanism of catecholamine secretion induced by histamine from the adrenal medulla and sympathetic noradrenergic neurones in the rat, and the role of capsaicin‐sensitive sensory nerves in this secretion. 2. Histamine at a dose of 1 mg/kg induced adrenaline and noradrenaline secretion by a non‐neurogenic mechanism. In contrast, at a dose of 3 mg/kg it induced adrenaline and noradrenaline secretion by both non‐neurogenic and neurogenic mechanisms. 3. The adrenaline released in response to histamine at 3 mg/kg was exclusively of adrenal origin whereas the noradrenaline released was of non‐adrenal origin (most probably noradrenergic sympathetic nerves). As with its action on the adrenal, histamine induced noradrenaline secretion from these extra‐adrenal tissues by both neurogenic and non‐neurogenic mechanisms. 4. When adrenaline secretion from the adrenal gland was impaired by adrenal denervation and/or adrenalectomy, the plasma noradrenaline secretion was increased. This is most probably due to compensation from the rest of the sympathetic nervous system. This compensatory increase in noradrenaline was abolished by hexamethonium, which indicates that it was mediated by a cholinergic mechanism. 5. Pre‐treatment of rats as neonates subcutaneously with capsaicin (a selective neurotoxin for certain sensory nerves) at a dose of 50 mg/kg, had no effect on the non‐neurogenic secretion of catecholamine induced by histamine. In contrast, capsaicin pre‐treatment abolished the neurogenic catecholamine secretion in response to histamine as well as the neurogenic compensatory increase in plasma noradrenaline levels that occurred when adrenaline secretion by the adrenal gland was impaired. 6. In the present study, by using histamine as a form of stress, we have been able to provide evidence not only (a) to confirm a role for capsaicin‐sensitive sensory fibres in modulating neurogenic adrenaline secretion from the adrenal gland, but also (b) to suggest a similar role for these fibres in modulating neurogenic noradrenaline release from sympathetic noradrenergic nerves in response to histamine and in response to impairment of adrenaline secretion by the adrenal gland.
Calcium‐activated inward current and contraction in rat and guinea‐pig ventricular myocytes.
Authors: Mitchell M R , Powell T , Terrar D A , Twist V W
Published: December 2014

1. Single ventricular cells from rat and guinea‐pig hearts were voltage clamped, and contraction was monitored with an optical method. 2. In rat cells, short (2‐10 ms) depolarizing pulses to 0 mV from a holding potential of ‐40 mV evoked current carried by calcium, and on repolarization to ‐40 mV there was a slow 'tail' current which decayed much more slowly than the expected deactivation of calcium current at this potential. 3. When rat cells were loaded with EGTA diffusing into the cytosol from an intracellular electrode, contraction and the tail current were both abolished, whereas the peak calcium current was not reduced. 4. Exposure of rat cells to ryanodine (1‐2 microM) suppressed both contraction and the tail current, but not peak calcium current. 5. The tail current was unaffected by tetrodotoxin (10 microM), but was reduced by lowering extracellular sodium to 10% by replacement with lithium or choline. 6. In rat cells, exposure to nifedipine (1‐5 microM) initially caused a marked reduction of calcium current while substantial contraction and tail current remained; longer exposure to nifedipine suppressed both contraction and the tail current. Isoprenaline (50‐100 nM) caused a marked increase in peak calcium current, while under these conditions there was little or no increase in either contraction or tail current. 7. The amplitude of the tail current in rat cells varied with the duration of the depolarization at 0 mV; the tail current evoked by repolarization to ‐40 mV reached a peak just as contraction was beginning to develop and was back to undetectable levels just as relaxation became significant, as might be expected if the tail current were determined by the cytosolic calcium transient which triggered contraction. 8. In guinea‐pig cells, a tail current was also recorded on repolarization to a holding potential of ‐40 mV, and, as in rat cells, the tail was suppressed by cytosolic EGTA and reduced by exposure of the cells to low‐sodium solution. 9. It is concluded that the tail currents recorded in both rat and guinea‐pig cells represent current activated by a rise in cytosolic calcium; in rat cells this is markedly dependent on ryanodine‐sensitive release of calcium from internal stores. The origin of this current, and its possible role during the plateaux of action potentials are discussed.
Sodium and potassium currents in acutely demyelinated internodes of rabbit sciatic nerves.
Authors: Chiu S Y , Schwarz W
Published: December 2014

1. Voltage‐clamp experiments were performed on single internodes isolated from rabbit sciatic nerve fibres acutely demyelinated with the detergent lysolecithin or a synthetic analogue, lysophosphatidyl choline palmitoyl. 2. The extent of demyelination was monitored by a gradual increase in the internodal leak conductance and capacitance. Voltage‐ and time‐dependent inward and outward currents, absent during the early phase (30‐40 min) of detergent treatment, appeared during the final phase (40‐60 min) of treatment. 3. The internodal ionic currents elicited by depolarizations consisted of three components pharmacologically identified as (a) a transient sodium current which was inhibited by tetrodotoxin, (b) a delayed rectifying potassium current which was inhibited by internal caesium and (c) a time‐dependent current that was abolished by replacement of external chloride with ascorbate. 4. The current‐voltage relations and h infinity curves for the internodal sodium current were similar in shapes to those of the nodal sodium current. 5. The amplitudes of the three internodal currents increased with the increase in the measured internodal capacity during the final phase of demyelination. 6. At high degrees of demyelination a peak sodium current of about 90 nA could be observed in an internodal segment of 100 micron length. 7. Interestingly, the membrane capacity measured at the time of such a large sodium current was about 10 times larger than could be accounted for by the axonal membrane in the recording pool alone. A suggestion is made that this represents lysolecithin‐induced membrane fusion between the Schwann cell and the internodal axon.