bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of guanidine on transmitter release and neuronal excitability.
Authors: Matthews G , Wickelgren W O
Published: December 2014

1. Guanidine hydrochloride (CH5N3‐HCl) was applied to frog neuromuscular junctions blocked by reduced external Ca2+, or increased external Mg2+ concentration, or by both. Guanidine produced a dose‐dependent increase in the average number of quanta released by presynaptic action potentials, the threshold dose being 0‐1‐0‐2 mM. No post‐synaptic effects were observed. 2. Guanidine also increased the excitability of the motor nerve fibres, as evidenced by multiple firing to single electrical stimuli and finally by spontaneous action potentials. These effects were studied in greater detail in giant axons (Müller axons) in the spinal cord of lamprey. Exposure to guanidine produced in these axons a progressive increase in excitability, manifested by repetitive firing to a single electrical stimulus, spontaneous membrane potential oscillations and spontaneous bursts of action potentials. Guanidine had no effect on the resting potential. 3. The effect of guanidine on the excitability of Müller axons was mimicked in every detail simply by reducing the divalent cation concentration of the bathing solution. 4. Guanidine also produced dose‐dependent increases in the duration of action potentials in Müller axons. This effect always preceded in time the appearance of the excitability effects and was not mimicked by reducing the divalent cation concentration. It is suggested that the broadening of the action potential is separate from the excitability effects and may reflect a decrease of delayed rectification. 5. Guanidine (0‐3 mM) increased the frequency of miniature end‐plate potentials (min. e.p.p.) in solutions containing 2‐11 mM‐K+ in such a way as to shift the relationship between min. e.p.p. frequency and extracellular K+ toward lower values of K+. This effect was interpreted to mean that guanidine produced a depolarization of the nerve terminal which summed with the depolarization produced by a given concentration of K+. The calculated depolarization produced by 0‐3 mM guanidine was 5‐7 mV. 6. The effects of guanidine on evoked transmitter release, excitability, and min. e.p.p. frequency are consistent with a hypothesis which states that guanidine binds at or near fixed negative changes on the outside of nerve membrane and reduces the screening effect of divalent cations.
Response of Aplysia statocyst receptor cells to physiologic stimulation.
Authors: Gallin E K , Wiederhold M L
Published: December 2014

1. The electrical responses of Aplysia statocyst receptor cells were investigated using intracellular micro‐electrodes. These ciliated mechanoreceptor cells were stimulated by downward tilting about a horizontal axis. 2. Tilting so that the receptor cell was excited produced a depolarizing receptor potential which, if large enough, could generate action potentials. 3. Large fluctuations in membrane potential were evident during depolarizing receptor potentials and were reduced or sometimes absent when a cell was tilted upward. Power‐density spectra of the noise voltage revealed that most of the energy added by downward tilt is contained in frequency components below 3 Hz. 4. Removing synaptic input to the receptor cells by cutting the statocyst nerve or adding excess Mg2+ to the bath did not abolish the increase in fluctuations caused by downward, excitatory tilts. 5. The depolarizing receptor potential was often associated with a decrease in membrane resistance as measured with constant current pulses using a bridge circuit. 6. Replacing most of the Na+ in the bath with either Tris or Mg2+ abolished both potential and resistance changes caused by downward tilt. These results indicate that an increased permeability to Na+ underlies the receptor potential.
Renin release and autoregulation of blood flow in a new model of non‐filtering non‐transporting kidney.
Authors: Sanowski J , Wocial B
Published: December 2014

1. A recently developed model of a non‐filtering, non‐transporting dog kidney, obtained by an in situ filling of tubules with low‐viscosity oil, was applied for studies of renin release and autoregulation of renal blood flow (RBF). 2. Renal blood flow was partially autoregulated after oil blockade of tubules, as indicated by a mean autoregulation index (Semple‐de Wardener (1959) of 0‐5. This was comparable to autoregulation of the stop‐flow kidney (index 0‐6) and contrasted with abolition of autoregulation after hypertonic mannitol loading at stop‐flow conditions (index 1‐1). 3. The aortic construction at a suprarenal level, which decreased renal perfusion pressure of the oil‐blocked kidney 35 +/‐ (S.E. of mean) 6 mmHg, produced an increase in arterial plasma renin activity of 1‐8 +/‐ 0‐1 ng. ml.‐1 (P less than 0‐02). Renin secretion rate decreased 33 to 70 ng.min‐1 in three dogs in which renal perfusion pressure was reduced to 60‐‐66 mmHg, but increased 110 +/‐ 41 ng.min‐1 when pressure reductions were kept within the renal blood flow autoregulation range (n=8, P less than 0‐025). 4. These results suggest that signals from the tubular receptor (macula densa) are not necessary for stimulation of renin release or autoregulation of renal blood flow.
Correlative physiological and morphological studies of rapidly adapting mechanoreceptors in cat's glabrous skin.
Authors: Iggo A , Ogawa H
Published: December 2014

1. A total of fifty‐four mechanoreceptor afferent units with fast conducting axons in the tibial nerve innervating the glabrous skin of the hind leg were isolated in anaesthetized cats. 2. Twenty‐six rapidly adapting units (RA), eighteen slowly adapting units (SA) and ten Pacinian corpuscle units (PC) were differentiated from each other mainly on the presence of the off response in RA and PC units to a ramp stimulation, the persistence of discharges of the SA units during steady pressure on the receptive field and the classical tuning curve seen in the PC units. A few PC units in the hairy skin were also studied for comparison. 3. Lamellated corpuscles were found histologically in the skin of the receptive field of RA units and identified as Krause's corpuscle of cylindrical type by their superficial location in the cutaneous tissue and their structure revealed by electron microscopy. 4. Physiological characteristics of RA units to various forms of mechanical stimulation were studied and compared with those of the other two kinds of units. SA units had the lowest critical slope among three groups and PC units the highest. 5. The discharge pattern of RA and PC units to a ramp stimulation was found to be time‐locked, whereas with SA unites only the first spike appeared at a fixed latency from the start of stimulation. 6. Some RA units showed a tuning curve which was flat from 10 to 200 Hz. Those with narrowly tuned curves had a best turning frequency at around 20 Hz. They were easily differentiated from the SA and PC units. SA units were tuned best at 5 HZ or less, and PC units at around 200 HZ. 7. The relation between the indentation velocity and amplitude of the ramp and the spike discharges was analysed in eleven RA units. In most cases the relation between identation velocity and maximum instataneous frequency was found to be best fit with a power function although other kinds of functions (linear, logarithmic, and logarithmic hyperbolic tangent) could also fit the relation at the 1% significance level. The instantaneous impuse frequency in RA units in response to various indentation amplitudes showed a step function. 8. The "off" responses to a ramp stimulation in RA units were also analysed in detail.
Metiamide and stimulated acid secretion from the isolated non‐distended and distended mouse stomach.
Authors: Wan B Y
Published: December 2014

1. The action of metiamide, a specific histamine H2‐receptor antagonist, on the acid secretory response to various gastric stimuli in the perfused isolated whole mouse stomach is described. 2. Two kinds of stomach preparations, the non‐distended stomach and distended stomach, were used. The distended stomach gave a marked and dose‐related acid secretory response to histamine (10(‐6) to 10(‐3) M), pentagastrin (10(‐8) to 10(‐5) M), acetylcholine (5 X 10(‐5) to 10(‐5) M), eserine (10(‐5) to 10(‐3) M) to dibutyryl cyclic AMP (5 X 10(‐5) to 10(‐3) M). In the nondistended stomach, dibutyryl cyclic AMP regularly stimulated acid secretion in a dose‐dependent manner; in contrast to dibutyryl cyclic AMP, histamine, pentagastrin or acetylcholine did not always stimulate acid secretion. 3. Histamine or pentagastrin but not acetylcholine always caused significant stimulation of acid secretion from the non‐distended stomach in the presence of a phosphodiesterase inhibitor such as caffeine, theophylline or the I.C.I. compound, 63197. At the concentration of 10(‐4) M, these phosphodiesterase inhibitors markedly potentiated the stimulatory effect of histamine or pentagastrin on acid secretion and the order of effectiveness was 63197 greater than theophylline greater than caffeine. 63197 also produced profound potentiation of histamine‐ or pentagastrin‐stimulated acid secretion in the distended stomach. 4. Metiamide (5 X 10(‐5) to 10(‐4) M) did not antagonize stimulation of acid secretion by dibutyryl cyclic AMP in the non‐distended or distended stomach. 5. In the distended stomach, metiamide (5 X 10(‐4) M) produced significant inhibition of histamine‐stimulated acid secretion with a linear and parallel displacement of the histamine dose‐‐response curve to the right. Although at this concentration metiamide did not depress maximal acid secretory response to histamine, it caused marked reduction of the maximal acid secretory response attainable with pentagastrin. 6. In the distended stomach, metiamide (5 X 10(‐5) M) did not cause significant inhibition of acetylcholine‐induced acid secretion. Atropine (5 X 10(‐6) M) abolished the stimulatory effect of acetylcholine; it also produced marked inhibition of pentagastrin‐stimulated acid secretion but it had little effect on acid secretion induced by histamine. 7. The present results indicate that metiamide inhibited histamine‐induced acid secretion by competitive antagonism of the histamine H2‐receptor, but its inhibitory effect on pentagastrin‐induced acid secretion seemed to be of non‐competitive nature. The failure of metiamide to inhibit acid secretion induced by dibutyryl cyclic AMP suggests that cyclic AMP might regulate gastric acid secretion at a site beyond the histamine H2‐receptor activation. It is also considered that the present results support the hypothesis that cyclic AMP may be involved in histamine‐ or pentagastrin‐induced acid secretion in the isolated mouse stomach. 8...
Eye‐ and head movements in freely moving rabbits.
Authors: Collewijn H
Published: December 2014

1. Eye‐ and head movements were recorded in unrestrained, spontaneously behaving rabbits with a new technique, based upon phase detection of signals induced in implanted coils by a rotating magnetic field. 2. Movements of the eye in space were exclusively saccadic. In the intersaccadic intervals the eyes were stabilized in space, even during vigorous head movements. Most of this stability was maintained in darkness, except for the occurrence of slow drift. 3. Many saccades were initiated while the head was stationary. They were accompanied by a similar, but slower head rotation with approximately the same amplitude. The displacement of the eye in space was a pure step without appreciable under‐ or over‐shoot. The deviation of the eye in the head was mostly transient. 4. Other saccades were started while the head was moving and were possibly fast phases of a vestibulo‐ocular reflex. The time course of the eye movement in space was identical for all saccades, whether the head was moving prior to the saccade or not. Eye movements without any head movement were not observed. 5. Saccades were mostly large (average 20‐6 +/‐ 12‐4 degrees S.D.) and never smaller than 1 degree. The relations of maximal velocity and duration to amplitude were similar to those reported for man. 6. Visual pursuit of moving objects, when elicited, was only saccadic and never smooth. 7. It is concluded that the co‐ordination and dynamics of the rabbit's head‐ and eye movements are similar to those of primates. In the absence of foveal specilization, the eye movements are restricted to a rather global redirection of the visual field, possibly in particular of the binocular area.
The passive electrical properties of frog skeletal muscle fibres at different sarcomere lengths.
Authors: Dulhunty A F , Franzini-Armstrong C
Published: December 2014

1. The passive electrical properties of frog skeletal muscle fibres have been measured at a number of different sarcomere lengths (from 2‐1 to 4‐0 micron). The geometrical outline of each fibre was determined from optical cross‐sections and sarcomere length was measured by laser beam diffraction. 2. When fibres were stretched to long sarcomere lengths the membrane capacity, Cm, of both normal and detubulated (glycerol‐treated) fibres was significantly less than the Cm of fibres at rest length. A significant reduction in membrane conductance of fibres held at long sarcomere lengths was only seen with detubulated fibres. 3. Membrane capacity and membrane conductance have a significant dependence on the cross‐sectional area of normal fibres but are independent of cross‐sectional area after detubulation. 4. It has been shown that membrane geometry depends on the sarcomere length of the fibre and it is suggested that the passive membrane properties are related to sarcomere length because they depend on membrane geometry. 5. The specific membrane capacity, calculated from the data from detubulated fibres, is 0‐8 micronF/cm2. 6. The internal resistivity, Ri, of normal fibres, also depends on sarcomere length between 2‐1 and 3‐0 micron. At a sarcomere length of 2‐1 micron the average Ri is 122 +/‐ 3 omega. cm (mean +/‐ S.E. of mean) and at a sarcomere length of 3‐0 micron the average Ri is 210 +/‐ 17 omega. cm (mean +/‐ S.E. of mean). No further increase in Ri was observed with further increases in sarcomere length.
Testicular blood flow and a study of the testicular venous to arterial transfer of radioactive krypton and testosterone in the rhesus monkey
Authors: Einer‐Jensen N. , Waites G. M. H.
Published: December 2014

1. Testicular blood flow (ml. 100 g−1.min−1; mean ±
S.E. of the mean) measured in monkeys by 133Xe clearance was 15·9 ± 1·2 (twenty‐six estimations on three monkeys; six testes) within 15 min of anaesthesia and 7·5 ± 0·8 (twelve estimates; four monkeys, eight testes), after 1‐2 hr of anaesthesia; and, when measured by 85Kr clearance in the second hour of anaesthesia was 9·1 ± 3·7 (seven estimates; four monkeys, four testes). Testicular temperature was 32·9 ± 0·2° C (mean ±
S.E. of mean) when deep body temperature was 37·2 ± 0·2° C.

2. Blood flow in the caput epididymidis was 27·4 ± 2·1 ml. 100 g−1.min−1 (mean ±
S.E. of mean; four estimates).

3. Radioactivity accumulated in the ipsilateral testis and epididymis but not in the contralateral tissues, during the infusion of 85Kr saline into the testicular veins.

4. During [3H]testosterone infusions into the testicular veins, radioactivity was consistently higher in ipsilateral testicular arterial plasma than in plasma withdrawn simultaneously from the aorta in four of five experiments with no difference in one. After two such infusions, the radioactivity was up to 5 times greater in the ipsilateral testis and epididymis than in the contralateral tissues.

5. During one infusion of [125I]bovine serum albumin into the testicular veins, there was no accumulation of radioactivity in the ipsilateral tissues.

6. Testosterone concentrations (ng.ml−1; mean ±
S.E. of mean) in plasma from seven anaesthetized monkeys which were sexually experienced were: testicular vein 53·22 ± 8·03 (eight estimates); testicular artery, 4·58 ± 0·94 (14); saphenous vein, 3·81 ± 0·68 (14). The corresponding values from four sexually inexperienced monkeys were 25·27 ± 2·11 (12); 2·89 ± 1·99 (12); aorta 2·76 ± 0·57 (12).

7. The results are discussed as evidence for vascular exchange of molecules between the testicular veins and artery in the spermatic cord.
Electrophysiological study of the antiluminal membrane in the proximal tubule of Necturus: effect of inorganic anions and SCN−
Authors: Anagnostopoulos Takis
Published: December 2014

1. A study has been made of the effects of anionic substitutions on the electrical potential difference (p.d.) and conductance characteristics of the antiluminal (peritubular) membrane of the proximal tubule of Necturus kidney. The tubular lumina were filled with oil in order to minimize potential and conductance contributions from luminal membrane and from paracellular shunt pathway.

2. Isosmotic substitutions, [A]o for [Cl]o, produced the following average changes in membrane p.d. (mV): F− +1·7, BrO3− +0·1, Br− ‐4·5, ClO3− ‐5·2, I− ‐7·9, NO3− ‐12·1, ClO4− ‐17·8, SCN− ‐25·3.

3. The amplitude of the depolarization caused by increase in K concentration (K‐depolarization) in the peritubular perfusate was found to increase during perfusion of the tissue with ClO4− (by 78%), SCN− (45%), I− (23%), NO3− (20%), Br− (16%); it decreased with F− (by 17%).

4. Comparison of membrane p.d. at peak K‐depolarization in the control state (during KCl perfusion) with that obtained in the experimental state (during KA perfusion) was found to be more reliable than determination of bi‐ionic potentials as a qualitative estimate of the permeabilities of the various anions (PA) relative to that of chloride (PCl).

5. Study of both peak K‐depolarization p.d. and bi‐ionic potentials yielded the following sequence for halide anion permeabilities: PF > PCl > PBr > PI. The peritubular membrane was found to be substantially more permeable to NO3−, ClO4− and SCN− than to Cl−.

6. The sequence of membrane conductances during anionic substitutions was Cl− ≃ BrO3− < Br− ≤ ClO3− < I− ≃ F− < NO3− < ClO4− < SCN−.

7. From the changes in p.d. induced by K‐depolarization, the absolute values of p.d. at peak K‐depolarization and from the changes in membrane conductance induced by anionic substitutions, it may be inferred that Br−, I−, NO3−, ClO4− and SCN− all increase PK; and that F− increases PNa (though a smaller increase in PK cannot be excluded).
Effects of sodium, potassium and calcium ions on the slow wave in the circular muscle of the guinea‐pig stomach
Authors: Ohba M. , Sakamoto Y. , Tomita T.
Published: December 2014

1. The contribution of Na, K and Ca ions to the generation of slow waves in the circular muscle of the guinea‐pig stomach was studied.

2. The slow waves had a lower, potential‐independent (first) and an upper, potential‐dependent (second) component. Reduction of the external Na prolonged the first component, but complete removal of Na depolarized the membrane and caused deterioration of the slow wave.

3. Readmission of Na (5‐10 m
M) restored the slow wave; this action was not abolished by ouabain.

4. Removal of K depolarized the membrane and slightly reduced the amplitude and duration of the slow waves. Readmission of K hyperpolarized the membrane and increased the amplitude and duration of the slow waves, particularly of the first component. Ouabain blocked the effects on the membrane potential, but not the effects on the slow waves.

5. An increase in extracellular Ca prolonged the first component and reduced the frequency. Removal of extracellular Ca abolished the slow wave activity. Excess Ca enhanced, and low Ca reduced the effects of altering the concentrations of external K.

6. It is concluded that the ouabain‐sensitive Na‐K pump may not be directly involved in generating slow waves, but that some other metabolic process is involved, which is regulated to a large extent by Ca, and possibly also by Na and K.
The action potential of chick dorsal root ganglion neurones maintained in cell culture.
Authors: Dichter M A , Fischbach G D
Published: December 2014

1. The directly evoked action potential of dissociated, embryonic, chick, dorsal root ganglion (DRG) neurones maintained in cell culture is prolonged compared to spinal cord cell spikes and the re‐polarization phase is marked by a plateau. 2. Evidence was obtained that both Ca2+ and Na+ carry inward current across the active soma membrane. Ca2+ because: overshooting spikes persist in tetrodotoxin (TTX) or Na+‐free media; in the presence of TTX (or absence of Na+) spike size varies directly with extracellular Ca2+ and spikes are eliminated by Co2+. Na+ because: spikes persist in the presence of Co2+ or Ca2+‐free media; in the presence of Co2+ (or absence of Ca2+) spike varies directly with extracellular Na+ and spikes are blocked by TTX. 3. On the other hand, Ca2+ plays less if any role in action potentials conducted along sensory nerve cell processes. Conducted spikes could not be evoked in TTX containing or Na+‐free media. 4. A long‐lasting depolarization follows the action potential in some neurones. This depolarization is associated with an increase in membrane conductance and appears to drive the membrane potential to ca. ‐30mV. It persists when conducted impulses are blocked so it is probably not a recurrent synaptic potential. 5. It is suggested that combined Ca2+‐Na+ spikes observed in isolated sensory neurones in vitro reflect the action potential of adult sensory cells but the possibility that they represent an early stage in development is also discussed.
Slow recovery of sodium current and 'gating current' from inactivation.
Authors: Meves H , Vogel W
Published: December 2014

1. Asymmetrical displacement currents ('gating currents') and Na currents have been recorded in intracellularly perfused squid giant axons with the voltage‐clamp method. Inactivation of the currents by a long‐lasting depolarization to ‐30 mV and subsequent removal of inactivation have been studied at temperatures of 0‐5‐3 degrees and 8‐9 degrees C. 2. The asymmetrical displacement current, recorded with the divided pulse procedure, was markedly reduced by a 1‐5‐800 msec depolarization to ‐30 mV; a 3 min depolarization led to almost complete blockage. 3. Recovery of the asymmetrical displacement current from a 3 min depolarization to ‐30 mV was slow (20‐40% recovery after 50‐800 msec at ‐70 mV and 8‐9 degrees C); full recovery from a long‐lasting depolarization took several minutes. 4. Recovery of the Na current followed a similar time course (20% recovery after 50‐800 msec at ‐70 mV and 8‐9 degrees C); the time constant of full recovery was 2‐3‐5 min. 5. Slow recovery was also demonstrated by recording the displacement currents associated with single depolarizing pulses. 6. The results are consistent with the idea that the asymmetrical displacement current is related to the function of the Na gates.
The effects of strontium and barium ions at synapses in sympathetic ganglia.
Authors: McLachlan E M
Published: December 2014

1. A study has been made of the effects of Sr2+ and Ba2+ ions at synapses in isolated superior cervical ganglia of guinea‐pigs. Intracellular recordings of membrane potential were made from ganglion cells in the presence of different concentrations of Ca2+, Sr2+ and Ba2+ ions. 2. The addition of Sr2+ (2‐5 mM) caused little change in resting membrane potential; in contrast, Ba2+ (1‐6 mM) always depolarized the cells and prolonged the duration of action potentials. 3. The resting frequency of spontaneous miniature excitatory post‐synaptic potentials (min. e.p.s.p.s) was briefly accelerated by the addition of either Sr2+ or Ba2+, but subsequently returned to about control levels. 4. Following replacement of Ca2+ by Sr2+, e.p.s.p.s could always be evoked during repetitive stimulation of preganglionic axons at a fixed latency after the nerve impulses ('phasic' transmitter release). Replacement of Ca2+ by Ba2+ produced many asynchronous e.p.s.p.s during trains of impulses ('residual' transmitter release). 5. By analysis of the interaction between Sr2+ and Ca2+, Sr2+ was shown to have a partial agonist action on 'phasic' transmitter release. The same analysis applied to Ba2+ failed to demonstrate either a partial agonist or antagonist action. 6. Both Sr2+ and Ba2+ prolonged e.p.s.p.s. Changes in Sr2+ could mainly be attributed to its effect on cell input resistance; Ba2+ may also prolong the time course of transmitter release. 7. The increased frequency of min. e.p.s.p.s which occurs during repetitive stimulation was potentiated by both Sr2+ and Ba2+, Ba2+ being about twice as potent as Sr2+. This activation of 'residual' transmitter release is independent of the action of these ions on 'phasic' release. 8. It is concluded that the reported maintenance by Ba2+ of acetyl‐choline output from perfused ganglia results from the asynchronous release of large numbers of quanta during trains of impulses.
Kinetic analysis and partitioning of sodium and chloride influxes across the gills of sea water adapted trout.
Authors: Girard J P , Payan P
Published: December 2014

1. Sodium and chloride influxes across the gills of sea water adapted trout were studied with the perfused isolated head technique. 2. The haemodynamic scheme describing anastomoses between efferent gill arteries and the filamentous sinus was confirmed and utilized to determine partitioning of sodium and chloride influxes. 3. Two routes of sodium and chloride entry were demonstrated, one lamellar and the other sinusal. The lamellar sodium and chloride fluxes are respectively 133+/‐21‐8 and 271+/‐43‐7 micronequiv/hr. 100 g. The sinus sodium and chloride fluxes are: 50+/‐18‐3 and 50+/‐11‐3 micronequiv/hr. 100 g. 4. The relative permeabilities of the apical and basal barriers of the lamellar epithelium were determined with influx experiments coupled to radioactive unloading experiments. The basal membrane is 30 times less permeable than the apical to sodium, while this ratio is 45 for chloride. Thus, the basal membrane represents the limiting factor in salt movement across the branchial epithelium. 5. The intracellular pools of the lamellar compartment were calculated for sodium: 1‐1+/‐0‐17 micronequiv/100 g of fish weight; and for chloride: 5‐1+/‐0‐83 micronequiv/100 g of fish weight.
Responses of spinocervical tract neurones to noxious stimulation of the skin.
Authors: Cervero F , Iggo A , Molony V
Published: December 2014

1. Activity of single spinocervical tract neurones has been recorded in the lumbar spinal cord of chloralose anaesthetized or decerebrated cats. Reversible spinalization was produced by cold block at L3. Sensitivity of these neurones to noxious stimulation was studied by heating their cutaneous receptive fields above 40‐45 degrees C. 2. Most of the units were located in lamina IV of the dorsal horn and had their receptive fields in the ipsilateral foot. All but one of the studied neurones were excited by moving hairs or by gentle mechanical stimulation of the skin. 3. Eighty‐four % of the units were affected by noxious stimuli and three kinds of response were obtained: (i) 61% were excited (E‐cells) by noxious heat; (ii) 19% were inhibited (I‐cells); and (iii) 19% gave a mixed response reversing from excitatory to inhibitory (EI‐cells). 4. E‐cells had axons with a wider range of conduction velocities than the rest and also received the strongest descending inhibition from supraspinal structures. 5. The recording sites of EI‐cells were located in the medial third of the dorsal horn whereas E‐ and I‐cells were distributed over the full width of the dorsal horn. 6. The possible role of the spinocervical tract in nociception is discussed.
Effects of prostaglandin antagonism on sodium arachidonate fever in rabbits.
Authors: Laburn H , Mitchell D , Rosendorff C
Published: December 2014

1. Sodium arachidonate, the prostaglandin precursor substance, when injected intraventricularly into rabbits, results in dose‐dependent hyperthermia, which is rapid in onset and of several hours duration. 2. Arachidonate fever was inhibited by intraventricular injection of indomethacin, but not by the simultaneous intraventricular injection of either of the two prostaglandin antagonists SC 19220 or HR 546. 3. Both antagonists effectively inhibited the fever induced by the intraventricular injection of an equipotent dose of PGE1. 4. Our results show that a derivative of arachidonic acid other than prostaglandin is pyrogenic.
Some electrophysiological properties of neurones of rat locus coeruleus.
Authors: Nakamura S
Published: December 2014

1. Electrical activity of neurones of the locus coeruleus (LC) was studied in rats anaesthetized with urethane. By stimulating the dorsal pathway (DP) of axons of LC neurones in the mid=brain and observing field responses in the dorsolateral tegmentum of the pons, micro‐electrodes were oriented to record unit discharges of LC neurones. They were evoked by DP stimulation mainly during the negative wave of the field response. 2. In the extraceullar records of spike discharges of LC meurones A and B spikes were distinguished. Very often the third component (C spike) was observed to ride on the descending stroke of the B spike. When present in the evoked discharge, it was also seen in the spontaneous discharge. 3. The DP‐elicited unit discharges of LC neurones were classified into three types. The type 1 response had a fixed latency and a distinct A‐B step. In the type 2 response the A spike occurred with a fixed latency, but the B spike followed it with variable delays, sometimes exceeding 5 msec. Being supported by the data of the collision test with spontaneous discharges, the type 1 and 2 responses were assumed to be due to antidromic excitation. The type 3 response whose characteristic was a wide variation of the latency from stimulation to stimulation was categorized as orthodromic excitation. Among seventy‐four responses, forty‐four were type 1, eight type 2 and twenty‐two type 3. The conduction velocities of axons of LC neurones, determined from the latencies of the A spike of the type 1 and 2 responses, ranged from 0‐3 to 1‐4 m/sec with a mean of 0‐69 m/sec. 4. Delay of the B spike in antidromic excitation was observed as a unique property of LC neurones. It was seen in the response to a single shock of DP (type 2 response) or in the response to the second shock of DP following the first one shortly (type 1 response). Since delay of the B spike in the type 2 response could not be ascribed to refractoriness, it was suggested that DP stimulation produced an inhibitory effect upon LC neurones. 5. LC neurones were invaded antidromically from the frontal or visual cortex, hippocampus, cerebellum or from varied combinations of them. About 70% of LC neurones were activated antidromically from the frontal cortex. The antidromic latencies ranged from 15 to 90 msec. 6. Some LC neurones were activated trans‐synaptically by stimulation of those forebrain sites which received axonal projections from LC. All LC neurones examined were excited trans‐synaptically by eletrical stimulation of the skin and the optic nerve. The sensory inputs arising from a vast area of the skin or those from the skin and the optic nerve were proved to converge on to the same LC neurones.
Gas deposition by counter‐current multiplication in the eel swim‐bladder: experimental verification of a mathematical model.
Authors: Steen J B , Sund T
Published: December 2014

1. Blood pO2 along the rete of eel has been investigated with a microelectrode, the swim‐bladder gas being replaced by air. 2. When the eel does not secrete gas, the pO2 profile is flat, whereas in actively secreting eel the pO2, along the rete has a maximum of approximately 1 atm near the bladder pole of the rete. 3. The findings confirm predictions of a mathematical model for counter current multiplication in the swim‐bladder.
Membrane properties of Aplysia neurones intracellularly injected with phospholipases A and C
Authors: Hinzen D. H. , Tauc L.
Published: December 2014

1. The effects of phospholipases A from bee venom and from porcine pancreas and of phospholipases C from Clostridium welchii and Bacillus cereus on active and passive membrane properties of Aplysia neurones have been studied. Consistent alterations in electrical membrane properties were found following intracellular application of three of these enzymes.

2. Bee venom phospholipase A produced a rapid decrease of membrane potential and resistance. Voltage clamping revealed a marked depression of peak transient current with little or no effect in the late outward current.

3. Mammalian phospholipase A was found ineffective in changing either the resting or active membrane properties.

4. Phospholipase C from Bacillus cereus led to a strong hyperpolarization and a fall in membrane resistance. Voltage clamping revealed a marked increase in the late outward current.

5. Neurones injected with Clostridium welchii phospholipase C manifested a several‐fold rise in resting membrane resistance as well as a tendency to slight hyperpolarization.

6. All enzymes were ineffective when externally applied.

7. It is tentatively concluded that the internally applied phospholipases affect specific ionic permeabilities both in the resting and active excitable membrane. Various mechanisms by which the differing actions of enzymes of the same type could be explained are discussed.
Maintained function of foreign and appropriate junctions of reinnervated goldfish extraocular muscle
Authors: Scott Sheryl A.
Published: December 2014

1. The ability of a multiply innervated muscle to become dually innervated, that is to accept a functional innervation from both its original and a foreign nerve, was investigated using the superior oblique muscle (s.o. muscle) of the goldfish.

2. Dual innervation of s.o. muscles was achieved by allowing the original nerve (cranial NIV) to regenerate to its s.o. muscle which had been previously denervated and cross‐innervated by a foreign nerve (cranial NIII), or by allowing the original and the foreign nerve to regenerate simultaneously to a denervated muscle.

3. Behavioural observations suggested that in some fish reinnervation of the s.o. muscle by its original nerve repressed the function of a previously established foreign innervation. However, physiological tests which involved the stimulation of both foreign and appropriate nerves, and the recording of mechanical and electrical activity of the s.o. muscle, demonstrated that there was no functional displacement of foreign innervation on these muscles, even on individual dually innervated fibres.

4. Dual innervation of the s.o. muscle persisted, apparently unchanged, for as long as the observations were continued (up to 7 months). The s.o. muscle contains two populations of fibres, fast and slow, and both types became and remained dually innervated.

5. When both NIII and NIV were allowed to regenerate simultaneously to a denervated s.o. muscle there was no obvious selectivity in the final pattern of innervation. On the average both nerves elicited approximately equal tension from s.o. muscles, and evoked excitatory junctional potentials (e.j.p.s) of similar mean quantal contents.

6. ‘Myotypic respecification’ was shown not to be responsible for the discrepancy between the behavioural results which sugested that repression of foreign innervation had occurred, and the physiological results which demonstrated that this was not the case. Anatomical and physiological findings indicated that the discrepancy was attributable to eye rotation produced by regenerated inferior oblique muscle fibres which contracted simultaneously with the cross‐innervated s.o. muscle. The net result was an eye movement in which the activity of the s.o. muscle was masked.

7. It is concluded that repression of established foreign neuromuscular connexions following reinnervation by the embryologically correct nerve does not occur on goldfish extraocular muscles. The s.o. muscle can become non‐selectively innervated by both foreign and appropriate axons, and remains so, at least for several months.
Reconstruction of the action potential of ventricular myocardial fibres
Authors: Beeler G. W. , Reuter H.
Published: December 2014

1. A mathematical model of membrane action potentials of mammalian ventricular myocardial fibres is described. The reconstruction model is based as closely as possible on ionic currents which have been measured by the voltage‐clamp method.

2. Four individual components of ionic current were formulated mathematically in terms of Hodgkin—Huxley type equations. The model incorporates two voltage‐ and time‐dependent inward currents, the excitatory inward sodium current, iNa, and a secondary or slow inward current, is, primarily carried by calcium ions. A time‐independent outward potassium current, iK1, exhibiting inward‐going rectification, and a voltage‐ and time‐dependent outward current, ix1, primarily carried by potassium ions, are further elements of the model.

3. The iNa is primarily responsible for the rapid upstroke of the action potential, while the other current components determine the configuration of the plateau of the action potential and the re‐polarization phase. The relative importance of inactivation of is and of activation of ix1 for termination of the plateau is evaluated by the model.

4. Experimental phenomena like slow recovery of the sodium system from inactivation, frequency dependence of the action potential duration, all‐or‐nothing re‐polarization, membrane oscillations are adequately described by the model.

5. Possible inadequacies and shortcomings of the model are discussed.
Relaxation experiments using bath‐applied suberyldicholine.
Authors: Adams P R
Published: December 2014

1. The effect of step changes in membrane potential on the end‐plate conductance change produced by bath‐applied suberyldicholine was studied in voltage‐clamped frog muscle fibres. 2. The suberyldicholine‐induced conductance increased exponentially from its previous equilibrium level to a new equilibrium level following a step hyperpolarization. 3. For low suberyldicholine concentrations the time constant of this relaxation was independent of the concentration. 4. For low suberyldicholine concentrations the voltage dependence of equilibrium conductance and relaxation time constants was identical. 5. Bungarotoxin pretreatment did not affect the responses beyond a simple reduction in their amplitude. 6. The conductance evoked by high suberyldicholine concentrations was less voltage‐sensitive than that evoked by low concentrations. 7. A new model for explaining noise and relaxation data is proposed. This postulates rate‐limiting binding steps followed by a voltage‐dependent isomerization.
Short‐circuit current and total conductance measurements on rabbit ileum.
Authors: Henriques de Jesus C
Published: December 2014

1. Short‐curcuit current (SCC) and total conductance (Gt) measurements were made in in vitro preparations of rabbit terminal ileum. 2. Successive additions of D‐glucose increased the SCC and Gt in a stepwise way and both effects were seen to correlate linearly. 3. Measurements of SCC ant Gt were also made after replacing Na in the Krebs solution by K or sucrose. The SCC decreased to nearly zero in both cases but the decrease in Gt was larger when sucrose was used. 4. SCC and Gt were monitored after the addition of ouabain. SCC decreased to nearly zero but Gt remained constant. 5. On successive additions of sucrose after the preparation was mounted in 1/4 Na Krebs without osmolal compensation, SCC decreased and Gt increased, a linear relationship being found between both changes. 6. Successive additions of 2‐deoxy‐td‐glucose caused a stepwise decrease of SCC and an increase in Gt. These effects seemed independent of the presence of glucose. 7. A model in which a resistance in series is added to the basic model by Ussing & Windhager (1964), modified by Rose & tschultz (1971), is proposed to account for these findings.
Ionic membrane conductance during the time course of the cardiac action potential.
Authors: Goldman Y , Morad M
Published: December 2014

1. Membrane ionic current‐voltage (I‐V) relations of the frog ventricular myocardium were measured during the action potential with a new single sucrose gap voltage clamp technique. 2. The I‐V relation is linear during the plateau and rapid repolarization phases of the action potential and during the development of the regenerative threshold of repolarization. 3. Time dependent I‐V relation during a series of voltage clamp pulses of clamp initiation. 4. The membrane conductance is remarkably constant during the plateau and is about 85 mumhos/muF of membrane capacitance. 5. Chloride conductance is about 18% of the total ionic conductance during the plateau and is not time dependent. Two inward Cl‐movement during a normal action potential is sufficient to approximately halve the action potential duration. 6. Membrane conductance did not change significantly when Ca2+ was omitted from the bathing medium. 7. Epinephrine increased the duration of the action potential and the total ionic conductance during the platiau in normal and Ca‐free media. 8. Separation of Na+ and K+ currents in muscles bathed in 'zero' Ca2+, 'zero' Cl‐ solution indicates that the inward and outward currents are balanced to within 2% during the slow repolarization. 9. The results indicates that a fine balance between conductance changes cardiac action potential. The possibility of a cross ionic interaction in the heart cell membrane is suggested.
The synergistic action of L‐glutamate and L‐aspartate at crustacean excitatory neuromuscular junctions.
Authors: Crawford A C , McBurney R N
Published: December 2014

1. When L‐glutamate and L‐aspartate are simultaneously applied to the excitatory neuromuscular junctions of Maia squinado, they produce an increase in the conductance of the post‐synaptic membrane much larger than the sum of conductance effects produced by the individual amino acids alone. 2. An examination of the synaptic noise occurring during this synergistic action reveals that the elementary conductnace events produced by aspartate are suppressed and that normal elementary conductance events produced by glutamate are occurring at an enormously increased rate. 3. It is suggested that aspartate causes this potentiation by inhibiting a system for transmitter inactivation in the region of the post‐synaptic receptors and that this system, under normal conditions, prevents the access of externally applied glutamate to the synaptic receptors.
Effects of innervation on the distribution of acetylcholine receptors on cultured muscle cells.
Authors: Anderson M J , Cohen M W , Zorychta E
Published: December 2014

1. Myotomal muscle cells from embryos of Xenopus laevis were cultured as a monolayer either alone or together with neural tube cells from the same embryos. 2. Spontaneous twitching and contractions evoked by electrical stimulation of neural perikarya were observed only in nerve‐contacted muscle cells, and could be abolished by curare or alpha‐bungarotoxin. 3. Within 2 days in culture muscle cells not contacted by nerve developed one or more discrete patches of acetylcholine (ACh) receptors as revealed by staining with fluorescent conjugates of alpha‐bungarotoxin. Similar patches were also seen when staining was carried out after paraformaldehyde fixation, suggesting that they were not induced by the dyetoxin conjugate. 4. Radioautography after labelling with [125I]alpha‐bungarotoxin revealed patches with grain densities approximately twenty‐five‐old greater than over the remainder of the cell. 5. Fluorescent stain on innervated cells was restricted to the path of nerve‐muscle contact and sometimes extended for greater lengths than the largest patches seen on non‐contacted muscle cells. 6. Similar long bands of stain associated with nerve‐‐muscle contacts were observed when cultures were grown in high concentrations of curare and carbachol which prevented spontaneous twitching. They were also seen in cultures in which the addition of neural tube cells was delayed for 2‐3 days. 7. It is concluded that innervation caused receptors to accumulate at sites of nerve‐muscle contact and that this process can operate independently of muscle activity.
Analysis of atropine action at the frog neutromuscular junction.
Authors: Feltz A , Large W A , Trautmann A
Published: December 2014

1. Atropine action on the end‐plate currents (e.p.c.s) has been analysed at the macroscopic and elementary levels. 2. The shortening effect of atropine on the e.p.c. and m.e.p.c. level can be fully explained by a reduction of the life time of the elementary current: this effect is markedly increased at more hyperpolarized membrane potentials and at higher concentrations of atropine. 3. It is therefore suggested that atropine binds to the open acetylcholine‐receptor complex, leading to a state with a null conductance. According to this model, the forward rate constant of atropine binding could be calculated and was of the order of 10(7) M‐1 S‐1 AT ‐90 MV and 20‐22 degrees C. 4. Although the conductance at the peak of the e.p.c. is reduced by atropine and becomes voltage sensitive, the elementary conductance is affected neither by voltage nor by atropine. 5. The exclusive binding of atropine to the activated ACh‐receptor complex, as proposed above, does not appear to explain this phenomenon. Another binding occurring before the channel is open with a dissociation constant of 60 micrometer could account for this effect.
Acetylcholine receptor distribution on myotubes in culture correlated to acetylcholine sensitivity.
Authors: Land B R , Podleski T R , Salpeter E E , Salpeter M M
Published: December 2014

1. A linear relation, with a slope of 0‐9 +/‐ 0‐2 on a log‐log plot, was obtained between acetylcholine (ACh) sensitivity and alpha‐bungarotoxin (alpha‐BTX) binding site density in developing L6 and rat primary myotubes. ACh sensitivity was defined as g/Qn where g is conductance, Q is ACh charge and n is the Hill coefficient. Experimentally we found n approximately 1‐7 for our myotubes, which is similar in value to that reported for adult systems. 2. The linear relationship is compatible with an organization whereby each ion channel is always complexed with a fixed number of ACh receptors such that the dose‐response characteristics of each such complex are independent of average ACh receptor density. 3. Light microscope autoradiography showed that the alpha‐bungarotoxin binding sites on L6 myotubes are uniformly distributed over the surface, while primary rat myotubes exhibit gradients and hot spots. Electron microscope autoradiography indicated that about 70% of the [125I]alpha‐bungarotoxin label was on the surface of the myotubes. The alpha‐bungarotoxin site density, after subtracting myoblast background, varied from 5 to 400 sites/micrometer2 on different L6 myotubes, and from 54 to 900 sites/micrometer2 on primary rat myotubes, with occasional hot spots of 3000‐4000 sites/micrometer2. The conductance sensitivities varied from 10(‐4) to 2 X 10(‐2) Momega‐1/nC1‐7.