bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversal of the physiological effects of brief periods of monocular deprivation in the kitten.
Authors: van Sluyters R C
Published: December 2014

1. Five normally reared kittens were monocularly deprived from day 32 to day 42 and then subjected to varying periods (from 6 to 14 days) of deprivation reversal using the technique of reverse suturing. Data obtained from single unit recordings in striate cortex of these kittens were compared to control data from seven normal kittens (aged 32 days to 22.5 weeks) and three normally reared kittens given monocular deprivation from day 32 to day 42. 2. Analysis of cortical ocular dominance patterns in these reverse‐sutured kittens revealed a progressively greater shift of influence away from the originally experienced eye and toward the originally deprived eye as the duration of the period of deprivation reversal increased. Most cortical cells were monocularly driven in these animals, but at each stage of the reversal process some binocular neurones were found. 3. The distribution of interocular differences in preferred orientation for binocular cells from these kittens was not significantly different from that for normal kittens, indicating that the pattern of connexions established by the originally deprived eye during reinnervation of striate cortex was very similar to that present before deprivation. 4. Previous studies on reversal of the effects of longer periods of monocular deprivation have indicated that during reinnervation of cortex by fibres representing the originally deprived eye an entirely new and different pattern of connexions is formed. On the basis of these results, it is hypothesized that short‐term monocular deprivation causes a reversible silencing of otherwise intact synapses, while terminals are physically disrupted when deprivation is prolonged. 5. This hypothesis is supported by the results of an additional set of experiments in which receptive fields, many of which were highly specific, could be demonstrated for about one‐half of the cells studied after removal of the non‐deprived eye in two normally reared kittens given 10 days of monocular deprivation beginning on day 32. Similar experiments in two kittens deprived from eye opening to day 42 revealed functional input to less than 20% of the cells studied and no evidence of response specificity.
Modulation of single vagal efferent fibre discharge by gastrointestinal afferents in the rat.
Authors: Davison J S , Grundy D
Published: December 2014

1. A single fibre dissection technique was used to record activity from efferent fibres in the left cervical vagus nerve of urethane anaesthetized rats. 2. The efferent discharge, in all units, was modulated by gastric inflation, gastric contractions or compression of the stomach wall. The receptors mediating these effects are the slowly adapting 'in‐series' tension receptors in the gastric musculature with afferent fibres in the vagus nerves. 3. Efferent units were classified according to their response to passive gastric distension and active gastric contractions. 4. Four distinct types of efferent unit were isolated. Type I units were excited and Type II units were inhibited by gastric distension and contraction. Type III units were excited at low or moderate levels of inflation and inhibited at high levels of inflation or during gastric contractions. Type IV units were inhibited by low levels of inflation but excited at higher levels. 5. Since there is clearly a reciprocal organization at least of some neurones in the vagal nucleus the possibility of reciprocal control of antagonist, cholinergic and 'purinergic' vagal pathways is discussed.
Intracellular studies of hair cells in the mammalian cochlea.
Authors: Russell I J , Sellick P M
Published: December 2014

1. Intracellular recordings were made from inner hair cells in the first turn of the guinea‐pig cochlea, the recording sites being confirmed by the injection of Procion yellow dye and subsequent histology. 2. The receptor potential, in response to a pure tone burst, consisted of an AC response which followed the wave form of the stimulus and was analogous to the extracellularly recorded cochlear microphonic and a depolarizating DC response which followed the envelope of the tone burst and was analogous to the extracellularly recorded summating potential. 3. The DC response was broadly tuned at high sound pressure having a maximal amplitude of 27 mV at a sound pressure level of ca. 100 db; however the bandwidth of the response was reduced at lower sound pressure level. Isoamplitude curves for the DC response were indistinguishable from the threshold curves for auditory nerve fibres. 4. The AC response was tuned in a similar fashion to the DC response except that it was attenuated at 6‐9 db/octave with respect to the DC response. It is suggested that this difference was due to the effect of membrane capacitance and resistance on the AC response. In contrast the extracellularly recorded AC component was not subject to this attenuation. 5. The total resistance and capacitance in three cells were found to be 46‐61 Momega and 7.8‐15.8 muF respectively. 6. Intracellular resistance changes were measured during sound stimulation, the resistance change being proportional to the DC receptor potential, indicating constant current flow through the hair cell. The current varied between 0.37 and 0.81 nA between cells. The time constant for seven cells was found to lie between 0.31 and 0.76 msec. 7. A map of the basilar membrane showing position of hair cells against characteristic frequency corresponded to the cut‐off frequencies of the basilar membrane mechanical measurements and the innervation sites of spiral ganglion cells.
The development of motor projection patterns in the chick hind limb.
Authors: Landmesser L
Published: December 2014

1. Retrograde transport of horseradish peroxidase was used to map the initial projection patterns of lumbosacral motoneurones to the embryonic chick hind limb. 2. The stage 28 segmental projection pattern to each of the four primary muscle masses was characteristic and indistinguishable from the stage 36 projection pattern to the sum of the muscles derived from that mass. In addition, the adductor motoneurone pool was found to be similar in position (both rostro‐caudal and mediolateral) at stages 29, 30, 32, 33 1/2 and 36. 3. Therefore axons from lumbosacral motoneurones project for the most part only to appropriate regions from early times shortly after they grow into the limb bud. Furthermore, the attainment of the segmental projection pattern occurs prior to the normal time of, and therefore without the aid of, cell death. This conclusion was supported by electrophysiological recordings made from muscle nerves. 4. A regionalization of the projection patterns within a single muscle mass could be shown both anatomically and physiologically prior to the cleavage of the mass into individual muscles and the projections were in a general way appropriate for the muscles derived from those regions. 5. Therefore the process of muscle cleavage does not in itself create the specific projection patterns observed, and motoneurone axons appear to grow to and to ramify and make synapses only within regions which correspond to their adult muscles. 6. Finally, the termination site of each motoneurone axon in the early limb was found to be tightly correlated in a somatotopic fashion with the position occupied by its soma in the cord. This suggests that some feature of the motoneurone related to its position may be of importance in achieving the specific projection patterns observed.
Influence of atrial stretch receptors on hypothalamic neurosecretory neurones.
Authors: Koizumi K , Yamashita H
Published: December 2014

1. The effects of stimulation of atrial receptors on hypothalamic neurosecretory cells were investigated in anaesthetized dogs and cats. Atrial receptors were activated by stretching the left and the right atria while action potentials of individual neurosecretory neurones in the supraoptic (s.o.n.) and paraventricular (p.v.m.) nuclei of the hypothalamus were recorded. 2. Stretching the left atrium markedly decreased firing frequencies of 'antidromically identified' s.o.n. and p.v.n. neurones in dogs and cats; 98% of neurones in dogs and 70% in cats were thus inhibited. Heart rate accelerated following a transient reflexly induced deceleration. The blood pressure was not affected. The magnitude and duration of inhibitory effects produced by atrial stretch on s.o.n. and p.v.n. neurones paralleled changes observed in heart rate. Approximately one third of 'unidentified' cells in s.o.n. and p.v.n. (those which could not be activated antidromically) were inhibited by left atrium stretch. 3. Bilateral vagotomy abolished the effects on neurosecretory neurones as well as on heart rate produced by left atrial stretch, indicating that the vagus nerves carry afferent impulses responsible for the observed changes. 4. Stretching the right atrium did not produce changes in firing frequencies of s.o.n. and p.v.n. neurones in dogs and cats, although cardiac rate was increased considerably by such stretch. Stimulation of the left and right atria was tested in the same animal in succession to permit comparison of the diverse results. 5. Interaction of responses originating from atrial receptors, baro‐ and chemoreceptors were studied. During carotid occlusion or stimulation of chemoreceptors activity of the neurosecretory cells was greatly augmented. Left atrial stretch when then applied evoked slight or no reduction in activity in s.o.n. and p.v.n. neurones. These results were interpreted to mean that the influence of baro‐ or chemoreceptors on neurosecretory neurones probably is stronger than that originating from atrial receptors. 6. Unlike the observations made in rats, no rhythmically bursting neurones (phasic cells) were found in dogs and cats. However, atrial stretch sometimes evoked a rhythmic bursting pattern which appeared only during stretch. 7. It is concluded that activation of left atrial receptors, through afferent impulses carried mainly by vagus nerves, inhibits neurosecretory neurones in s.o.n. and p.v.n. The implications of this finding in relation to the role of ADH in the maintenance of blood volume control were discussed.
A study of the factors responsible for rate‐dependent shortening of the action potential in mammalian ventricular muscle.
Authors: Boyett M R , Jewell B R
Published: December 2014

1. An intracellular micro‐electrode was used to record action potentials from superficial cells of a cat papillary muscle during isometric contractions. The muscle was stimulated regularly and test stimuli were interpolated at various times between regular (control) responses. 2. The duration of test action potentials (measured at 80% repolarization) increases exponentially with time as the interval between the test stimulus and the preceeding stimulus is increased and a curve drawn through the data reaches a plateau at test intervals of 1.0‐1.5 s. This curve is considered to reflect the time course with which membrane conductances return to their pre‐stimulus values after a control response, and it is known as the 'electrical restitution curve'. 3. At much longer test intervals the action potential duration duration increases again and it approaches the rested state value of about 0.5 s when the interval between stimuli is 200‐300 s. 4. Interventions that raise the peak tension developed in isometric contractions, such as an increase in the rate of stimulation or in the bathing calcium concentration, displace the electrical restitution curve downwards (to shorter action potential durations) and to the left (to shorter stimulus intervals). This shift in the curve is accompanied by a reduction in its magnitude (i.e. the difference in duration between the earliest possible action potential and the plateau value), but the interventions differ in their effects on the time course of electrical restitution: an increase in stimulus frequency causes a marked slowing, whereas an increase in bathing calcium concentration produces a slight speeding up of its time course. 5. The reduction in action potential duration produced by an increase in stimulus frequency (rate‐dependent shortening) can be separated into two components, one resulting from the downward displacement of the electrical restitution curve and the other depending on the time available between consecutive responses for membrane recovery. The second component becomes increasingly important at stimulus frequencies above 100 min‐1. 6. Changes in action potential duration observed during the tension staircases produced by regular stimulation of a rested preparation and by paired pulse stimulation can also be accounted for by interaction of downward displacement of the electrical restitution curve and variations in the degree of recovery of the membrane between consecutive responses. 7. Downward displacement of the electrical restitution curve is thought to result from intracellular accumulation of calcium and/or extracellular accumulation of potassium, and the available evidence is considered to favour the former mechanism.
Electrical property and chemical sensitivity of vascular smooth muscles in normotensive and spontaneously hypersensitive rats.
Authors: Kuriyama H , Suzuki H
Published: December 2014

1. The membrane properties and sensitivity to chemical substances of smooth muscle cells of the portal vein and pulmonary artery were studied in normotensive rats (Wistar Kyoto) and spontaneously hypertensive rats (Okamoto & Aoki) by the micro‐electrode method. 2. The parameters of the membrane, i.e. resting membrane potential, the maximum rate of rise of the spike, space constant of the tissue and time constant of the membrane measured from the portal vein were the same in normotensive rats (less than 120 mmHg) and spontaneously hypertensive rats (greater than 165 mmHg). Similar results were also obtained from the pulmonary artery. Such findings indicate that the passive electrical properties of the vascular muscle membrane are not involved in the generation mechanism of hypertension. 3. In the portal vein the maximum slope of the membrane depolarization produced by tenfold increase in external K+ concentration expressed on a logarithmic scale was the same in normal and hypertensive rats (42 and 41 mV, respectively). These observations were confirmed by the effects of application of excess K+ on the pulmonary artery (48 mV in normal and 46 mV in hypertension). With a low concentration of K+, the membrane was depolarized to a greater extent in the portal veins than in the pulmonary arteries of both types of rats. Although the response to K+ differed in vascular muscles excised from the different regions, no functional difference was apparent between normotensive and hypertensive. 4. In both portal vein and pulmonary artery, the smooth muscle membrane of spontaneously hypertensive rats proved to be more sensitive to noradrenaline, i.e. depolarization of the membrane appeared with noradrenaline 10(‐9) g/ml. in hypertensive but with 10(‐8)g/ml. in normotensive rats. Depolarization block of the spike generation appeared at a slower concentration of noradrenaline in hypertensive rats. Sensitivity of the smooth muscle membrane to prostaglandin E2 in the portal vein was also higher in hypertensive rats. 5. The present results indicate that the only difference between normal and spontaneously hypertensive rats regarding smooth muscle cell membrane of the pulmonary artery and portal vein is increased chemical sensitivity in hypertensive rats, and the passive electrical properties of the membrane probably does not contribute to the generation of hypertension.
Compound action potentials recorded from mammalian peripheral nerves following ligation or resuturing.
Authors: Davis L A , Gordon T , Hoffer J A , Jhamandas J , Stein R B
Published: December 2014

1. Cat hind limb peripheral nerves were fitted with cuff recording electrodes, and their distal portions were later cut and ligated to prevent regeneration. The compound action potential amplitude initially declined with a time constant between 1 and 2 months and then remained relatively unchanged for periods of more than a year. Similar but smaller changes were observed in the conduction velocity of the nerves which also stabilized after a few months. 2. In nerves that were cut and resutured to their distal stumps or sutured directly to nearby muscles, a recovery was observed. The time course was well fitted by an initial exponential decay with a similar time constant to that above, followed by an exponential recovery with a longer time constant (3‐4 months). Nerve conduction, muscle potentials and twitch tension often recovered to control values, even when the amplitude of the nerve compound action potential remained depressed. 3. Thus, nerve fibres survive axotomy for long periods of time and continue to conduct action potentials, even if unable to regenerate to appropriate end‐organs. When regeneration is permitted, a fraction of nerve fibres may reinnervate nearly all end‐organs. The diameter and conduction velocity of these nerve fibres presumably increase toward control values, while other fibres remain subnormal in these parameters. 4. Factors in the design of cuff electrodes which determine the amplitude of compound action potentials are described in an Appendix.
Potassium currents in frog ventricular muscle: evidence from voltage clamp currents and extracellular K accumulation.
Authors: Cleemann L , Morad M
Published: December 2014

1. The single sucrose voltage clamp technique was used to control the membrane potential of strips of frog ventricular muscle and to measure the membrane current. The extracellular K accumulation was estimated from the after‐potential observed after the release of the voltage clamp. 2. Comparing the time course of the membrane current to the time course of the development of the after‐potential at different membrane potentials, it was found that all slow current changes are related to changes in the K current across the membrane. 3. Based on measurements of membrane current and the after‐potential, the total membrane current was separated into two fractions: (a) the K current which gives rise to K accumulation and (b) the residual membrane current which is unrelated to K accumulation. The current‐voltage relation for the residual membrane current is linear or slightly inwardly‐rectifying. Residual current is zero at the resting potential and increases to about 1 microamperemeter/cm2 at ‐20 mV. 4. The measured membrane currents and after‐potentials indicate qualitative differences between the K currents which dominate below and above ‐20 mV. More negative to ‐20 mV the after‐potential develops rapidly while at potentials positive to ‐20 mV the after‐potential develops with some delay. 5. The current dominating below ‐20 mV is inwardly‐rectifying. The current‐voltage relation has a maximum (about 2 microamperemeter/cm2) and a region with marked negative slope conductance. The outward current in the region of negative slope conductance is increased with increasing [K]o. 6. A model for the inwardly rectifying K current is described. The model accurately reproduces the shape of the measured current‐voltage relations and their modification by alterations in the extracellular K concentration. The model is also compatible with the observation that all slow current changes below ‐20 mV are directly related to K accumulation. 7. The K current which dominates at potentials positive to ‐20 mV is activated by a potential and time dependent process which is unrelated to extracellular K accumulation. 8. Q10 for the magnitude of the inwardly rectifying K current is about 1.35 while the Q10 for the rate of increase of the time dependent K current is about 3‐‐4. 9. Cs blocks the inwardly recitfying K current but has little effect on the time dependent K current. 10. The changes in the action potential duration caused by increasing the extracellular K concentration or addition of Cs to the perfusate can be explained by the effect of K and Cs on the inwardly rectifying K current.
Efferent control of stimulus access to the hamster vomeronasal organ.
Authors: Meredith M , O'Connell R J
Published: December 2014

Previous workers had identified the vomeronasal organ, on anatomical evidence, as an accessory olfactory organ, present in most terrestrial vertebrates. Lesion experiments had demonstrated its importance in sexual behaviour in the hamster. Howevever, the sequestered position of the vomeronasal receptor epithelium within the organ raised questions concerning the access of olfactory stimuli. Using electrophysiological and pharmacological methods we have now demonstrated the following. 1. A pumping mechanism exists, powered by vasomotor movements, which can suck stimulus substances into the vonmeronasal organ. 2. A mechanism also exists for the active expulsion of the contents of the vomeronasal organ. 3. These mechanisms are activated by fibres running in the nasopalatine nerve. 4. The suction mechanism is controlled by sympathetic, probably adrenergic, fibres from the superior cervical sympathetic ganglion. Control of the expulsion mechanism has not been definitely established but does not appear to be sympathetic. 5. The vomeronasal organ can be adequately stimulated by activation of the pumping mechanism in the presence of odour. 6. Odour responses of single units in the accessory olfactory bulb have been recorded for the first time. 7. The time course of neuronal response in the accessory olfactory bulb is more rapid than predicted by many authors. The response is sufficiently fast that the vomeronasal system cannot be ruled out as a possible sensory pathway in many odour related behaviours. Possible modes of action of the pumping mechanism in awake animals are discussed.
Serotonergic innervation of the locus coeruleus from the dorsal raphe and its action on responses to noxious stimuli.
Authors: Segal M
Published: December 2014

The connexions between the dorsal raphe nucleus and the nucleus locus coeruleus were studied in urethane anaesthetized rats. 1. Cells in the locus coeruleus gave an excitatory response to a noxious stimulus, e.g. leg pinch. 2. This excitatory response was blocked by either a parenteral or an ionophoretic injection of morphine and recovered after an injection of naloxone. 3. Electrical stimulation in the region of the dorsal raphe blocked excitatory locus coeruleus responses to noxious stimuli. 4. While naloxone did not antagonize the effects of the dorsal raphe stimulation towards locus coeruleus activity, these effects were absent in rats pretreated with a serotonin synthesis inhibitor, PCPA or with 5,7‐DHT which destroys serotonin‐containing terminals, and were reduced by the serotonin antagonist methysergide. 5. A serotonin‐containing inhibitory pathway between the dorsal raphe and the locus coeruleus is proposed to account for these results.
Vestibulo‐ocular function during co‐ordinated head and eye movements to acquire visual targets.
Authors: Barnes G R
Published: December 2014

1. Experiments have been conducted on human subjects in an attempt to establish the role of the vestibulo‐ocular reflex in the co‐ordination of head and eye movements during visual target acquisition. 2. When the subject moved head and eyes to acquire visual targets in the horizontal plane, the eye movement consisted of an initial saccade in the direction of head movement followed by a slower return towards orbital centre which compensated for remaining head movement. 3. When the head was moved either voluntarily or passively in the dark the pattern of eye movement was very similar to that seen during target acquisition. 4. The mean latency between the start of head acceleration and the onset of the saccadic eye movement was greater in the dark (108 msec, S.D. 85 msec) than for the visually induced responses (14 msec, S.D. 59 msec), in which eye movement often preceded head movement when moving to small ( less than 45 degrees) target offset angles. 5. In all experimental conditions gaze displacement at the end of the initial saccade was normally related in a predictive manner to final head position, but when fixating visual targets offset by more than 60 degrees from the central position there were often large errors, 22% of responses undershooting the target by more than 15 degrees. 6. A highly significant (P less than 0.001) linear relationship was found between gaze displacement and head velocity under all experimental conditions. During target acquisition head velocity was normally positively correlated with amplitude of target offset. The large errors in gaze displacement in response to the larger target offsets occurred at levels of head velocity lower than normally associated with such target offsets. 7. The results have led to the suggestion of a dual mode of control for head‐eye co‐ordination. In one mode, normally associated with small target offsets (less than 45 degrees), control is mediated by retinal error information. In the other mode, associated with larger target offsets, gaze displacement is generated as an automatic response to head turning. 8. The observation of similar relationships between head and eye movement during passive head turning implicates the vestibulo‐ocular reflex in the secondary mode of control, and provides support for the hypothesis that the role of the vestibular saccade is to induce a rapid offset of the eyes in the direction of head movement, thus facilitating rapid search and target location.
The effect of carbon dioxide upon myocardial contractile performance, blood flow and oxygen consumption.
Authors: van den Bos G C , Drake A J , Noble M I
Published: December 2014

1. Mongrel dogs were anaesthetized with chloralose, paralysed, ventilated and vagotomized and given a beta‐blocking drug, sotalol, in sufficient doses to block the effects of 5 microgram of adrenaline. 2. Changes in inspired CO2 concentration were produced, causing increases of arterial PCO2 up to 120 mmHg. The effects on myocardial blood flow were measured with radioactive microspheres. Coronary sinus and arterial blood was sampled. 3. In the absence of beta‐blockade, an increase in arterial PCO2 produced variable effects. In some dogs coronary blood flow increased, while in others there was no change. There was a mean increase in coronary blood flow at arterial PCO2 values above 85 mmHg which was abolished by beta‐blockade. 4. In the presence of beta‐blockade, an increase of arterial PCO2 produced depression of left ventricular performance, i.e. a fall of maximum rate of rise of left ventricular pressure and a rise of left ventricular end‐diastolic pressure. 5. In the presence of beta‐blockade, there were no consistent changes in myocardial blood flow, left ventricular pressure or cardiac output. 6. In the absence of beta‐blockade, coronary arterial minus venous ocygen content was reduced by hypercapnia. In the presence of beta‐blockade, the changes were small and not statistically significant. The direct coronary vasodilator effect was therfore negligible. 7. It is concluded that the previously reported hypercapnic vasodilatation was mainly an effect of sympatho‐adrenergic stimulation by hypercapnia. 8. In the presence of beta‐blockade, coronary sinus PO2 increased markedly, with little change in coronary sinus oxygen content; this was consistent with a shift to the right of the oxy‐haemoglobin dissociation curve. Under circumstances of hypercapnia, a rise in coronary sinus (and presumably tissue) PO2 failed to produce vasoconstriction. 9. It is argued that the vasodilator effect of hydrogen ions and the vasoconstrictor effect of oxygen probably cancel one another when the arterial PCO2 is raised.
Sympathetic control of lower oesophageal sphincter motility in the cat.
Authors: Gonella J , Niel J P , Roman C
Published: December 2014

1. The action of adrenaline, noradrenaline and efferent sympathetic fibres on the smooth muscle of the lower oesophageal sphincter (l.o.s.) was studied in vivo on the anaesthetized cat and in vitro with the sucrose gap method. 2. Adrenaline and noradrenaline produce a marked depolarization of the circular muscle of the l.o.s. This effect is suppressed by dihydroergotamine or phentolamine, and greatly reduced by atropine; it remains unaltered by hexamethonium. 3. Sympathetic fibres are excitatory for the l.o.s. They come from the stellate ganglion or run along the splanchnic nerve: the fibres arising from the stellate ganglion (mainly by the cardiac branch of the ganglion) join the vagus nerve at the thoracic level; the fibres running along the splanchnic nerve pass through the coeliac ganglion without synapsing; their cellular bodies lie probably in the ganglia of the sympathetic chain. 4. Repetitive stimulation (20‐‐40 Hz) of these fibres induce, with a latency of 5‐‐8 sec, a sustained or rhythmic contraction of the l.o.s. This response is suppressed by dihydroergotamine, and greatly reduced by atropine, while hexamethonium has no effect. 5. Stimulation of sympathetic fibres induces a facilitation of the vagal excitatory responses and an inhibition of the vagal inhibitory responses of the l.o.s. 6. Our data show that the sympathetic response of the l.o.s. results from the stimulation of adrenergic receptors which are located not only on muscular fibres but also, and chiefly, on intrinsic neurones. Thus, the sympathetic control of the l.o.s. is mainly exerted through cholinergic myenteric neurones which could be excited either directly or indirectly by inhibition of inhibitory intrinsic neurones.
Identification of different sodium compartments from smooth muscle cells, fibroblasts and endothelial cells, in arteries and tissue culture
Authors: Garay R. P. , Moura Anne Marie , Osborne-Pellegrin Mary J. , Papadimitriou A. , Worcei M.
Published: December 2014

1. The 22Na efflux curve from the rat tail artery, at 35 °C, can be analysed as the sum of three distinct components, from 0 to 90 min of washout. After an initial diffusional component the two late exponential components Be−kBt and Ce−kCt have the following values: B = 3·03 ± 0·15 m‐mole/kg wet wt. and C = 0·56 ± 0·04; kB = 0·145 ± 0·005 min−1 and kC = 0·015 ± 0·007.

2. In order to identify the cellular origin of the different compartments we compared the 22Na efflux curve from the rat tail artery with the curves obtained from whole rabbit aortal strips, rabbit aortal medial or adventitial strips; and primary cultures from rabbit aorta medial smooth muscle cells, cultures of a non‐fusing muscle cell line (BC3H1), fibroblasts and endothelial cells.

3. It is possible to identify under these experimental conditions the cellular compartments from which the different exponential components of the efflux from the whole arteries originate. Fibroblasts and endothelial cultures, as well as adventitial strips exchange 22Na slowly with exponential constants resembling kC. Their efflux rate constants are: fibroblast cultures 0·010 ± 0·002 min−1, endothelial cells 0·015 ± 0·003 min−1 and adventitia 0·019 ± 0·007 min−1. Smooth muscle cells are exclusively responsible for the intermediate component Be−kBt, but they present also a slow component, indistinguishible from the slow exponential component from the other types of cells in the artery. The rate constants for muscle cells are: rabbit aortic media kB 0·25 ± 0·09 min−1 and kC = 0·013 ± 0·004 min−1; medial cultures kB = 0·202 ± 0·005 min−1 and kC1 = 0·020 ± 0·003 min−1; and BC3H1 cell culture kB = 0·205 ± 0·083 min−1 and kC = 0·016 ± 0·003 min−1.

4. The efflux from compartment B of smooth muscle cells is inhibited by ouabain and in the absence of extracellular K+. The efflux from compartment C is inhibited only by ouabain but not by the suppression of extracellular K+.

5. We propose a distribution of Na+ in smooth muscle cells in two intracellular compartments: (1) Na+ freely dissolved in the sarcoplasm, exchanging with the kinetics of compartment B and (2) a second cellular compartment which could be contained in the sarcoplasmic reticulum exchanging with the kinetics of compartment C.

6. On the basis of the previous model of Na+ distribution, considering our values, and without any correction, the estimated sarcoplasmic concentration of Na+ is 9·6 m
M, compatible with the direct measurements obtained in skeletal and heart muscle. The Na+ concentration in the sarcoplasmic reticulum would be 4‐10 times higher than in the cytoplasm. In order to increase the accuracy of our calculations it would be necessary to account for the interdiffusion and back diffusion of Na+ between compartments. It is not possible to attain this goal at the present time.
Some properties of the excitatory junction potentials recorded from saphenous arteries of rabbits.
Authors: Holman M E , Surprenant A M
Published: December 2014

1. Excitatory junction potentials (e.j.p.s) were recorded from smooth muscle cells of the saphenous arteries of young rabbits. 2. The amplitudes of e.j.p.s recorded from different preparations, in response to a single maximal stimulus, were small and variable (5‐‐14 mV). They decayed exponentially with a time constant of about 200 msec. 3. At frequencies greater than 1 Hz the shape of those e.j.p.s which exceeded 12‐‐15 mV in amplitude was changed. The early part of the e.j.p.s became faster in time course. 4. Trains of up to five stimuli, at frequencies greater than 4 Hz, caused summation of e.j.p.s; 'active responses' were superimposed on this depolarization. Peak amplitude of the response to repetitive stimulation was 50 mV. 5. In normal solution, contraction appeared to be associated with a change in the configuration of e.j.p.s. 6. No action potentials resembling those recorded from most visceral smooth muscles were observed in normal solutions although these could be evoked in the presence of TEA (2.5‐‐10 mM). 7. The method of Abe & Tomita (1968) was used to determine the values of the length constant (lambda) and time constant (tau) of the smooth muscle of intact arteries. The value of lambda (0.6 mm) was about half that found for circular strips cut from larger arteries. 8. The time constant of decay of single e.j.p.s of less than 12 mV in amplitude was indistinguishable from the membrane time constant. 9. Noradrenaline caused contraction of the artery in the absence of a change in membrane potential. 10. It is tentatively suggested that there may be two different populations of receptors in this smooth muscle membrane.
Ionic currents in response to membrane depolarization in an Aplysia neurone.
Authors: Adams D J , Gage P W
Published: December 2014

1. Action potentials recorded in the soma of R15 neurones in the abdominal ganglia of Aplysia juliana were not suppressed by selective inhibition of either Na or Ca conductance alone. It was necessary to block both conductances to suppress action potentials. 2. Membrane currents generated by step depolarizations of the soma consisted of early transient and delayed steady‐state currents. The early transient current could have one or two components depending on the activating depolarization. 3. The early more rapid component had a reversal potential at +54 mV and the reversal potential changed with extracellular Na concentration in accord with the Nernst equation. It was blocked by substitution of impermeant cations for Na, by TTX and by internal injections of Zn. It was concluded that this component was normally a Na current. 4. The later slower component of the transient current had a reversal potential at about +65 mV and the reversal potential changed with extracellular Ca concentration is accord with the Nernst equation. It was blocked by substitution of Mg for Ca or addition of Mn, Co, Ni or verapamil to the extracellular solution. It was concluded that this component was normally a Ca current. 5. Na and Ca currents were generated at different threshold potentials, Na currents first appearing at about ‐20 mV and Ca currents at ‐5 to 0 mV. 6. The time‐to‐peak of both Na and Ca currents was affected by the holding potential, by the amplitude of the activating depolarization, by temperature and by divalent ion concentration. 7. The peak Na and Ca conductances both increased sigmoidally with increasing depolarization, the maximum Na conductance of 10‐‐15 microS being approximately twice the maximum Ca conductance. Peak conductances for Na and Ca reached half‐maximum at ‐8 and +3 mV, respectively. 8. The amplitude of the delayed steady‐state current could be varied by changing the extracellular K+ ion concentration or by adding tetraethylammonium to the extracellular solution. The reversal potential for 'tail currents' was ‐67 mV and shifted 18 mV when the extracellular K concentration was doubled. It was concluded that the delayed steady‐state current was K current. 9. With prolonged depolarizations, K current decayed with a time constant of the order of 1 sec. Peak K conductance increased with increasing depolarization with the half‐maximum occurring at a potential more positive than +20 mV. The maximum rate of fractional activation of K conductance was independent of the amplitude of the clamp step.
Open loop increase in trunk temperature produced by face cooling in working humans.
Authors: Cabanac M , Caputa M
Published: December 2014

1. Five human subjects pedalled on a bicyle ergometer for at least two 74 min periods at 10 degrees C ambient temperature. During the first period the subjects cycled for 42 min with face fanning, followed by 32 min with the head thermally insulated. In the second period, this procedure was reversed. Oesophageal (tes), tympanic (Tty), forehead and hand skin temperatures were recorded. In addition, heart rate (H.R.) was counted throughout the experiments, and the technique of perceptual rating of cool and warm stimuli was used in order to appreciate whether the subjects were hypo‐, normo‐, or hyperthermic. 2. Face fanning resulted in decreased Tty, decreased H.R., mild skin vasoconstriction but increased Tes. 3. Head covering resulted in increased Tty and H.R., while Tes decreased slightly, due to peripheral vasodilatation. 4. When their faces were being fanned so that Tty was low and Tes was high, the subjects gave slightly hypothermic ratings. Ratings were clearly hyperthermic when their heads were covered and Tty was high and Tes was low. 5. The close correlation between vasomotor response and H.R. on the one hand and Tty on the other confirms that this variable is a better approximation of regulated core temperature than Tes. 6. Increase in Tes during face fanning and decrease in Tes during face insulation is new evidence for the possibility of the human brian being cooled during exercise by cool blood returning from the face. 7. We suggest that this selective brain cooling determines the apparent upper resetting of core temperature during exercise while brain temperature remains precisely regulated and constant.
Membrane potential, contractile activation and relaxation rates in voltage clamped short muscle fibres of the frog.
Authors: Caputo C , Fernandez de Bolaños P
Published: December 2014

1. Voltage clamped short (approximately 1.5 mm) muscle fibres of the frog can develop maximum tension of 4.3 kg/cm2. 2. The time course of contractile responses to prolonged depolarization is markedly dependent on the fibre membrane potential. With sufficiently long pulses the responses present a plateau and a spontaneous relaxation phase. 3. At room temperature (20‐‐22 degrees C), and at membrane potentials of ‐10 mV the plateau duration is about 2 sec and the spontaneous relaxation rate is 0.50 sec‐1. At membrane potentials of ‐35 mV the plateau duration is 4.6 sec and the spontaneous relaxation rate is 0.28 sec‐1. 4. When the fibres are depolarized at room temperature with relatively short pulses (less than 2 sec), the contractile responses are cut short at the end of the pulse, and the fibres relax at a rate (11 sec‐1) which is independent on the pulse amplitude and duration. 5. The relaxation rate after a short pulse can be affected by membrane potential only in the region near the contractile threshold where further release of contractile activator is expected to occur. 6. The time course of contractile responses to prolonged depolarization may be shortened by conditioning depolarization. 7. The system responsible for the release of contractile activator may be tentatively described by three states, resting, activated, and inactivated, in analogy with the model proposed by Chandler, Rakowski & Schneider (1976) to describe the possible configurations of the potential dependent charge movement in muscle.
Reflex connexions of motoneurones of muscles involved in head movement in the cat.
Authors: Rapoport S
Published: December 2014

1. The reflex connexions from muscle afferents and ventral root fibres to the motoneurones of the muscles biventer‐cervicis, complexus, sternocleidomastoid, trapezius and splenius, the principal muscles involved in head movement in the cat, were studied with the technique of intracellular recording. 2. Electrical stimulation of homonymous muscle afferents of biventer‐cervicis and complexus, sternocleidomastoid and trapezius, at strengths below 1.6 times threshold of the dorsal root afferent volley, produced monosynaptic e.p.s.p.s in the corresponding motoneurones. Recruitment of higher threshold muscle afferents produced additional p.s.p.s with longer central delays. 3. Stimulation of low‐threshold muscle afferents did not produce any p.s.p.s in the motoneurones of the ipsilateral antagonist. Stimulation of higher threshold afferents evoked i.p.s.p.s with central delays longer than 1.6 msec, or mixed e.p.s.p.‐i.p.s.p.s in the ipsilateral antagonist. 4. Mixed e.p.s.p.‐i.p.s.p.s or i.p.s.p.s with central delays longer than 1.5 msec were evoked in trapezius motoneurones upon stimulation of high threshold afferents from biventer‐cervicis and complexus, while stimulation of low‐threshold biventercervicis and complexus afferents evoked no p.s.p.s in trapezius motoneurones. 5. Stimulation of contralateral low‐threshold biventer‐cervicis and complexus afferents evoked a sequence of i.p.s.p. disinhibition in sternocleidomastoid motoneurones, and vice versa, with central delays longer than 1.7 msec. 6. Stimulation of the deafferented biventer‐cervicis, complexus, splenius, sternocleidomastoid and trapezius muscle nerves frequently activated interneurones in the ventral horn at monosynaptic central delays. Activation of homoynmous ventral root fibres rarely evoked p.s.p.s in biventer‐cervicis, complexius, splenius or sternocleidomastoid motoneurones, while it produced disynaptic i.p.s.p.s in 80% of trapezius motoneurones. 7. It is concluded that Ia reciprocal inhibition and recurrent inhibition, two reflex circuits which are so prominent in limb segments of the spinal cord, do not play a major role in the generation of head movement. Rather, head movement may be primarily controlled from supraspinal centres.
The central control of the lumbar sympathetic pathway to the large intestine of the cat.
Authors: De Groat W C , Krier J
Published: December 2014

1. The origin of the lumbar sympathetic inhibitory outflow to the large intestine was studied by recording simultaneously changes in colonic motility and efferent firing in the lumbar colonic nerves (l.c.n.) following lesions at various levels of the neuraxis. 2. Multiunit recordings from the l.c.n. usually consisted of irregular grouped discharges which were unrelated to spontaneous colonic contractions or to respiratory or cardiac cycles. The firing was depressed by the administration of ganglionic blocking agents or by decentralization of the inferior mesenteric ganglion, indicating that it was post‐ganglionic and primarily central in origin. 3. In the majority of experiments colonic motility and l.c.n. firing were not altered by transection of the cervical (C2‐C3) or thoracic (T10‐T13) spinal cord. However, in these acute spinal animals destruction of the lumbar ventral roots or the lumbar spinal cord markedly enhanced colonic motility and depressed l.c.n. firing. These findings indicate supraspinal mechanisms are not essential for the generation of the lumbar inhibitory outflow to the colon. 4. Transection of the l.c.n. enhanced colonic motility in animals with an intact neuraxis, in acute spinal animals and in animals where the thoracolumbar sympathetic outflow was blocked. It is concluded that peripheral ganglionic as well as spinal pathways can sustain an inhibitory input to the colon. 5. L.c.n. firing was enchanced by stretching or pinching the proximal colon or small intestine or by electrical stimulation of intestinal afferent fibres (Adelta and C fibres) in the l.c.m. and mesenteric branches of the splanchnic nerves. The reflexes occurred via spinal pathways and were blocked by transection of the lumbar dorsal roots. Spontaneous firing in the l.c.n. was also generated by isolated segments of the lumbar spinal cord; however, this firing occurred independently of traditional reflex pathways since it was uanffected by transection of the lumbar dorsal roots. It is concluded that the spontaneous firing must be generated via ventral root afferent pathways or via endogenous oscillator circuits in the lumbar spinal cord.
The kinetics of iron uptake in vitro by human duodenal mucosa: studies in normal subjects.
Authors: Cox T M , Peters T J
Published: December 2014

1. A method for determining initial rates of unidirectional radio‐Fe uptake from a ferric chelate of nitrilotriacetic acid by human duodenal biopsy specimens in vitro has been devised. [57Co]cyanocobalamin was used as an extracellular fluid marker, and was shown to give results in close agreement with other markers. 2. Uptake was linear for up to 20 min and exhibited saturation kinetics over the concentration range 18‐‐450 mumole/1. 3. In the presence of 2:4 dinitrophenol and fluoride, uptake was reduced by approxi‐50%, indicating dependence on metabolic energy. 4. Uptake of Fe was markedly diminished at reduced incubation temperatures, demonstrating a high activation energy for the uptake process. 5. Many of the criteria for the demonstration that the initial uptake of Fe depends on an active transport mechanism have been fulfilled. 6. The apparent distribution volume of 14C‐labelled nitrilotriacetate chelate did not exceed the extracellular fluid space, suggesting that Fe is transferred to specific receptors on the enterocyte. The findings are discussed in relation to the possibility that uptake may be a rate‐controlling step for the regulation of net intestinal absorption of Fe in man.
Tetanus toxin and synaptic inhibition in the substantia nigra and striatum of the rat.
Authors: Davies J , Tongroach P
Published: December 2014

1. The effects of tetanus toxin were determined on GABA‐mediated synaptic inhibition of substantia nigra neurones evoked by striatal stimulation and on the presumed dopamine‐ and 5‐hydroxytryptamine‐mediated synaptic inhibition of striatal neurones evoked by nigral and dorsal raphe nucleus stimulation, respectively, in the urethane‐anaesthetized rat. 2. Following an intranigral injection of tetanus toxin, striatal‐evoked inhibition of substantia nigra neurones, which is sensitive to bicuculline, was rapidly abolished. This effect was not accompanied by any significant change in the responses of nigral neurones to ionophoretically administered GABA or other putative neurotransmitters and thus indicates a presynaptic site of action of the toxin. 3. The rate of onset of action of the toxin in the substantia nigra was extremely rapid (1‐4 min) and appeared to be related to the rate of activation of the inhibitory pathway. 4. Injections into the substantia nigra of tetanus toxin neutralized with antitoxin had no significant effect on striatal‐evoked inhibition in the substantia nigra. 5. Injections of tetanus toxin into the striatum failed to influence the inhibition of striatal neurones evoked by stimulation of the ipsilateral substantia nigra or the dorsal raphe nucleus, suggesting that tetanus toxin does not impair monoamine‐mediated inhibition in the central nervous system. 6. Synaptic excitation which preceded substantia‐nigra‐evoked inhibition in striatal neurones and which occasionally preceded striatal‐evoked inhibition in nigral neurones was also unaffected by tetanus toxin. 7. It is suggested that tetanus toxin selectively abolishes GABA‐mediated synaptic inhibition in the central nervous system and may be a useful tool in the identification of such synaptic inhibitory mechanisms.