bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of prolonged depolarization on synaptic transfer in the stellate ganglion of the squid
Authors: Katz B. , Miledi R. 
Published: December 2014

1. Depolarization of the giant axon terminal of the squid causes local calcium influx which gives rise to transmitter release and post‐synaptic response, and which under certain experimental conditions leads to a regenerative action potential in the presynaptic terminal itself.2. There has been conflicting evidence in the literature on the question whether the calcium permeability change in the terminal is rapidly inactivated, or whether it can persist with little diminution for hundreds of milliseconds during a depolarizing voltage step.3. Results are presented which show that there is little ‘calcium inactivation’, even when very large depolarizing steps are imposed on the terminal and maintained for periods of 1‐2 sec.4. Contrary indications are examined and found to be attributable to an increase of potassium conductance, rather than direct inactivation of calcium conductance.
Factors in cerebrospinal fluid from goats that affect sleep and activity in rats*
Authors: Fencl V. , Koski G. , Pappenheimer J. R. 
Published: December 2014

1. Intraventricular infusion in the rat of 0·1 ml. cerebrospinal fluid (c.s.f.) from sleep‐deprived goats increases the duration of sleep (measured by e.e.g.) and decreases locomotor activity (measured photo‐electrically) for at least 6 hr subsequent to the infusion. Subarachnoid infusions are ineffective.2. C.s.f. from control and sleep‐deprived goats was fractionated by ultrafiltration through molecular sieves. The sleep‐promoting Factor S is found in the low molecular weight fraction (mol. wt. < 500) of c.s.f. from sleep‐deprived but not from control goats.3. The concentration of Factor S in c.s.f. increases progressively during the first 48 hr of sleep deprivation.4. The sleep promoting effects of Factor S cannot be duplicated by serotonin, 4‐OH‐butyrate, butyrolactone, GABA (γ‐amino butyric acid), glutamic acid or 3′,5′‐cyclic AMP when these substances are added to control fluids in concentrations up to 10 times greater than those found in normal c.s.f.5. Intraventricular or subarchnoid infusion in the rat of 0·1 ml. proteinfree c.s.f. containing molecules in the mol. wt. range of 500–10,000 at 10–30 × normal concentration causes hyperactivity which persists for several days and nights following the infusion. The excitatory material, probably a peptide, is present in c.s.f. from both control and sleep‐deprived goats.6. The properties of Factor S suggest that it may play a role in the normal regulation of sleep and wakefulness.
The hypothalamic neurosecretory pathways for the release of oxytocin and vasopressin in the cat
Authors: Bisset G. W. , Clark Barbara J. , Errington M. L. 
Published: December 2014

1. The neurones of the supraoptic nucleus (SON) and paraventricular nucleus (PVN) were stimulated electrically in lactating cats under chloralose anaesthesia. Milk‐ejection responses were used to monitor the release of oxytocin and vasopressin and both hormones were assayed in samples of blood collected during stimulation. The position of the tip of the stimulating electrode was confirmed from brain sections stained selectively for cystine‐rich neurosecretory material.2. A previous finding that stimulation of the SON in the cat releases vasopressin without oxytocin was confirmed.3. Stimulation of the PVN caused both hormones to be released. The ratio of their concentrations in blood was variable; this suggests release from separate neurones.4. Both hormones were also released on stimulation of the median eminence but not of the zone lying vertically between this structure and the PVN. No neurosecretory material was detected in this zone. These findings argue against the existence of a direct or medial paraventriculo‐hypophysial pathway running downwards along the wall of the third ventricle.5. Study of sections from unstimulated brains confirmed that the tractus paraventricularis cinereus of Greving which runs ventro‐laterally from the PVN towards the SON, represents the principal efferent pathway for neurosecretory fibres from the PVN.6. The results are discussed in relation to the problem of the independent release of oxytocin and vasopressin in response to physiological stimulation of the neurohypophysis.
Spontaneous and evoked activity of neurones in the somatosensory thalamus of the waking cat
Authors: Baker M. A. 
Published: December 2014

1. Adult cats were prepared for chronic micro‐electrode recording in the nucleus ventralis posterolateralis (VPL) of the ventrobasal complex (VB) of the thalamus. Spontaneous and evoked activity of single neurones was recorded extracellularly while the animal stood in a hammock. The behavioural state of the animal and the electroencephalogram (e.e.g.) were observed and recorded.2. Three hundred and twenty‐five single neurones sensitive to movement of hairs, depression of skin or movement of claws were isolated and studied. Peripheral receptive fields were on the contralateral surface of the body. They remained constant in size and location over long periods of time and despite changes in the behavioural state of the animal. Most of the receptive fields covered a cutaneous area at least as large as an entire paw and many covered an entire limb and extended on to the trunk. These fields are larger than those described by other investigators using natural stimulation in anaesthetized or paralysed animals.3. Moving hairs or touching skin in the peripheral receptive field elicited a burst of spikes at frequencies between 100 and 150/sec. Repeated stimulation did not result in obvious alteration or habituation of the response. There was no apparent change in responsiveness of neurones to peripheral stimulation when the animal was asleep.4. Except for claw‐sensitive units, all neurones were active in the absence of intentional stimulation of the receptive field. When the animals were awake, VPL neurones fired more regularly than during sleeping. In slow sleep, with e.e.g. slow waves and spindles, firing patterns were characterized by the presence of more high‐frequency bursts of spikes and more long interspike intervals than in waking. Claw‐sensitive units, silent during waking, fired in bursts during sleep. When small doses of barbiturate were injected intravenously while recording the activity of neurones, the firing pattern changed to one in which all of the activity occurred in the form of high‐frequency bursts. Interburst intervals were variable.5. The level of spontaneous activity in VB in conscious cats is greater than in sensory and sensorimotor cortex to which it projects. The pronounced effect of behavioural state on spontaneous activity of these neurones suggests that the background activity in somatosensory systems may play some role in the processing of afferent input.
Analysis of the potential‐dependent changes in optical retardation in the squid giant axon
Authors: Cohen L. B. , Hille B. , Keynes R. D. , Landowne D. , Rojas E. 
Published: December 2014

1. An analysis has been made of the change in optical retradation of the membrane elicited by the application of voltage—clamp pulses in squid giant axons.2. The retardation response consists of three separate voltage—dependent components. For freshly mounted axons, defined as being in state 1, hyperpolarizing pulses give a rapid increase in the light intensity measured with crossed polarizers which has been termed the fast phase. This is followed by a rather slow return towards the base line termed the rebound. On treatment of the axon with certain agents that include tetrodotoxin, high calcium and terbium, the rebound disappears and the fast phase slows down, increases in size, and has a new slow component added to it. This transition from state 1 to a second state, 2, appears to be irreversible.3. In state 1, the time constant of the fast phase is 20–40 μsec at 13° C; it has a very large negative temperature coefficient (Q10 = Ca.⅛). The size of the retardation change is independent of temperature and varies as the square of the applied voltage, but the voltage—retardation curve is symmetrical about a point well beyond zero membrane potential, at an internal potential of around + 70 mV. In state 2, the time constant is about five times larger, and varies much less markedly with temperature; the apex of the voltage—retardation curve is shifted to + 200 mV.4. The rebound has a time constant of the order of 20 msec at 13° C. A 10° rise in temperature more than halves the time constant and roughly doubles the amplitude of the rebound. The voltage dependence of the rebound differed from that of the fast phase.5. The slow component of state 2 has a time constant of about 2 msec which does not change noticeably between 10 and 25° C. The size of this component seems to be linearly dependent on the applied voltage, rather than obeying a square law.6. A tenfold increase in external calcium concentration had no discernible effect on the fast and slow phases, but reversibly reduced the amplitude of the rebound nearly to half.7. In experiments on perfused axons, the retardation response was not measurably altered by any of the modifications made to the composition of the perfusing fluid.8. There was some indication of the possible existence of a small current‐ or conductance‐dependent component of the retardation response.9. These phenomena seem likely to originate either from molecular relaxation processes analogous with the Kerr effect, or from changes in membrane thickness under the influence of the pressure exerted by the electric field. However, the specific molecules involved in the retardation response cannot yet be identified.
The effect of different ionic levels on the electrical response of toad skin to noradrenaline
Authors: House C. R. 
Published: December 2014

1. After the addition of noradrenaline (final concentration 4 × 10−5
M) to the inner medium of isolated toad skins, they underwent a depolarization (inner surface becoming less positive) followed by a hyperpolarization.2. The dependence of the minimal and maximal levels of the depolarizing and hyperpolarizing phases of the response upon the external concentrations of sodium and chloride ions was examined.3. The experimental data were considered to support the view that the hyperpolarization was generated by an increase in the sodium to chloride permeability ratio for the outer barrier of the skin and that the depolarization resulted from a transient increase in the conductance of transient shunt pathways in the skin.4. When the external sodium and chloride ions were replaced by magnesium (or potassium) and sulphate ions, noradrenaline initiated a transient hyperpolarization. During this hyperpolarizing response the time course of the change in the skin's conductance resembled that of the skin potential. The polarity of the response was changed by reversing the chloride concentration gradient across the skin.5. The dependence of the maximal level of the hyperpolarizing response upon the internal potassium concentration was examined.6. It was concluded that the hyperpolarizing response was generated partially by an increase in the potassium to chloride permeability ratio for the inner barrier of the skin and predominantly by the movement of chloride and accompanying cations through a transient shunt pathway, probably the active glands.
Effects on body temperature of prostaglandins of the A, E and F series on injection into the third ventricle of unanaesthetized cats and rabbits
Authors: Milton A. S. , Wendlandt Sabine 
Published: December 2014

1. Prostaglandins were injected into the third ventricle of unanaesthetized cats and rabbits whilst rectal temperature was recorded.2. In cats prostaglandin E1 and E2 (PGE1 and PGE2) produced hyperthermia which mostly began within a minute of injection and lasted 1 or more hours. With PGE1 the hyperthermia was shown to be dose dependent between 10 ng and 10 μg (2·8 × 10μ11 and 2·8 × 10−8
M). The hyperthermia was associated with vigorous shivering, skin vasoconstriction and piloerection. In several experiments a secondary rise in temperature occurred a few hours after the injection but such an effect was sometimes observed with control injections of 0·9% NaCl solution as well.3. None of the other prostaglandins (A1, F1α, F2α) examined in cats had an immediate or strong effect on temperature comparable to the hyperthermia produced by PGE1 and PGE2.4. In rabbits PGE1 (2 μg) also caused hyperthermia which began shortly after the injection and lasted for hours. PGF2α and PGA1, did not affect temperature.5. In cats it was seen that an intraperitoneal injection of 4‐acetamidophenol (paracetamol 50 mg/kg) did not affect the initial strong hyperthermia produced by PGE1 and PGE2 but abolished the secondary rise.6. The possibility is discussed that PGE1 plays a role as a central transmitter or modulator in temperature regulation.
The permeation of several materials into the fluids of the rabbit's brain
Authors: Davson Hugh , Welch Keasley 
Published: December 2014

1. 24Na, 36Cl and 35S thiourea were infused
I.V. in rabbits according to schedules designed to yield approximately level activity in plasma for periods up to 5 hr. Cerebrospinal fluid was sampled before ending the experiment by decapitation and the radioactivities in cerebrospinal fluid and in homogenized brain were compared in each case to a time weighted mean value for plasma.2. The results are considered in terms of a simplified model which specifically acknowledges the continuity of the extracellular and cerebrospinal fluids and thus the coupling between processes which occur at the interfaces bordering those fluids.3. From the rate constants for exchange across the blood—brain interface that were necessary for simulation of the observed behaviours, permeability coefficients for that interface were estimated for the materials studied and, from experiments of others, for 42K.
Depolarization of the tooth pulp afferent terminals in the brain stem of the cat
Authors: Davies W. I. R. , Scott D. , Vesterstrøm K. , Vyklický L. 
Published: December 2014

1. Tooth pulp afferent fibres belonging exclusively to the Aδ group were stimulated bi‐polarly with electrical pulses applied to the dentine and the central effects of the stimulation were examined in the nucleus of the spinal trigeminal complex of anaesthetized cats.2. Field potentials evoked by single pulses to the upper or lower canine tooth pulp were explored over the nucleus of the spinal trigeminal tract in the region 5 mm caudally to the obex up to 8·5 mm rostrally to the obex. They were found to be restricted to a region of 5·5–8·5 mm rostrally to the obex, 4‐5 mm laterally from the mid line, with a maximum amplitude at a depth of 5 ± 0·5 mm.3. Antidromic action potentials were recorded from the tooth pulp afferents. The stimulating micro‐electrode was inserted in the region of the medulla from which distinct field potentials could be recorded by orthodromic stimulation.4. Excitability of the central terminals of the tooth pulp primary afferents was increased when the test stimulus was preceded either by a conditioning volley in low threshold afferent fibres of the infraorbital nerve or in Aδ fibres of another tooth.5. Single pulses applied to the afferent fibres of the tooth pulp produced changes in the excitability of central terminals of the fast conducting afferent fibres of the infraorbital nerve.6. The greatly increased excitability of central terminals of tooth pulp primary afferent fibres was accompanied by a small decrease in their synaptic efficiency as estimated from the changes of the post‐synaptic component of the field potential evoked by their stimulation.7. It is concluded that an analogous presynaptic control mechanism is present at the central terminals of the tooth pulp primary afferent fibres as is known for the fast conducting cutaneous system. But a difference in the specifity of the action from this afferent system is suggested. While activity from Aα fibres is very effective in evoking primary afferent depolarization at both fast conducting trigeminal fibres and slow conducting Aδ system, the Aδ fibre activity is effective only at the latter, and not at the former.
The action of carbon dioxide on synaptic transmission in the cuneate nucleus
Authors: Morris Mary E. 
Published: December 2014

1. The excitability of synaptic structures in the cuneate nucleus was studied in eighteen decerebrate, unanaesthetized cats during acute changes in inspired PCO2.2. Micro‐electrode stimulation in the caudal half of the cuneate nucleus evoked antidromic and orthodromic responses which were recorded simultaneously from a forelimb nerve and from the medial lemniscus at the transected mid‐brain surface.3. Increases in the concentration of inspired CO2 (2–20%) progressively decreased the direct excitability of both the afferent fibre terminals (reflected in the antidromic potentials) and the cuneate relay neurones (reflected in the α wave of the orthodromic lemniscal response). Synaptically mediated responses, recorded as the β component of the lemniscal potentials, were also depressed.4. The relation between input and output at the cuneate was determined by plotting antidromic against trans‐synaptic (β lemniscal) responses for different intensities of stimulation. The mean slope for logarithmic values of control potential amplitudes was 1·17 (±
S.E. 0·13). It therefore appears that the transfer function for the cuneate is linear over a wide range.5. In the majority of experiments the input—output relation was unchanged or increased by raising PCO2. It was concluded that the efficiency of synaptic transmission and release of transmitter appeared to be well maintained or possibly increased at individual active synapses during hypercarbia.6. The depressant action of CO2 on afferent transmission can therefore be attributed largely to a block of impulse conduction in the primary afferent fibres.
Depolarization and calcium entry in squid giant axons
Authors: Baker P. F. , Hodgkin A. L. , Ridgway E. B. 
Published: December 2014

1. Changes in ionized calcium in giant axons were followed by recording the light produced by injected aequorin.2. From the effect of injecting calcium buffers the internal concentration of ionized calcium was found to be about the same as in a mixture of 45 Ca EGTA:55 free EGTA, i.e. about 0·3 μ
M.3. After an axon had been exposed to cyanide for 50–100 min the velocity of the aequorin reaction increased about 500 times. This effect, which could be reversed rapidly by removing cyanide, was probably brought about by release of calcium from an internal store.4. Injecting 30 μmole ATP per litre of axoplasm into a cyanide‐poisoned axon caused a transient lowering of light intensity; oligomycin blocked the effect.5. Raising external calcium or replacing external sodium by choline or lithium reversibly increased the light produced by axons injected with aequorin.6. Stimulation at 50–200 impulses/sec in a solution containing 112 m
M‐Ca caused the light intensity to increase to a new steady level; after stimulation the light intensity returned to its original level with a time constant of 10–30 sec. Similar but smaller effects were seen in solutions containing less external calcium. The recovery after stimulation is probably due to uptake of calcium by the internal store.7. Injecting 3 m‐mole EGTA per litre axoplasm lowered the resting glow and abolished the aequorin response to stimulation.8. There was no light response to stimulation immediately after an axial injection of aequorin and the effect increased to a ‘steady’ level with a half‐time of about 5 min. The conclusion is that the rise in calcium concentration resulting from stimulation is confined to the peripheral part of the axon and that the diffusion coefficient of aequorin in axoplasm is about 4 × 10−7 cm2/sec.9. The increment in light per impulse often increased markedly during the course of a long experiment and there was also considerable variation between axons.10. If the light response to stimulation was small it was proportional to the frequency of stimulation; if large to the square of the frequency.11. Voltage‐clamp experiments showed that the calcium entry associated with a depolarizing pulse could be divided into an early component which was abolished by tetrodotoxin (TTX), and a late component which was unaffected by this inhibitor.12. The time relations of the early calcium entry were consistent with its being a leak of calcium ions through the sodium channel; the permeability of the sodium channel to calcium was about 1% of the permeability to sodium.13. The late entry of calcium was little changed by injecting enough tetraethylammonium (TEA) to block the outward potassium current; it was greatly reduced by external concentrations of manganese which had little effect on the maximum potassium conductance.14. The voltage—response curve for the late entry of calcium had a well defined maximum and was similar in shape to the curve relating calcium entry to depolarization at the presynaptic ending (Katz & Miledi, 1969, 1970).
Myoepithelial cell activation in the submaxillary salivary gland
Authors: Darke A. C. , Smaje L. H. 
Published: December 2014

1. Pressure in the duct of the submaxillary gland of the cat was recorded under chloralose anaesthesia. Single pulses applied to the parasympathetic nerve caused a pressure rise.2. Salivation was just detectable in about half of the animals when an open tube was connected to the duct and single pulses applied to the nerve. Applying a back pressure of 1‐4 mm Hg renders the duct less distensible and under these circumstances secretion of 1‐3 μl. fluid was always seen. An alternative method of detecting salivation based on the pressure record itself also showed that salivation occurred in response to the stimulus and that salivation was responsible for the pressure rise observed.3. Single pulses applied to the cervical sympathetic trunk produced a small fall in pressure. In a short series of pulses this was followed by a slow rise which then slowly decayed. It was tentatively concluded that the initial fall was secondary to the accompanying vasoconstriction but the subsequent effects were due to myoepithelial cell contraction.4. Close arterial injection of bradykinin caused a pressure rise which could best be explained by myoepithelial cell contraction.5. It is concluded that the myoepithelial cells of the submaxillary gland of the cat do not receive a parasympathetic motor innervation but it is probable that they are innervated by the sympathetic nervous system and contract in the presence of bradykinin.
The detection of gratings in narrow‐band visual noise*
Authors: Carter Barbara E. , Henning G. Bruce 
Published: December 2014

1. The detectability of sinusoidal gratings comprised of either one or many cycles was measured in veiling luminances the spatial frequencies of which were either narrow‐ or broad‐band.2. In narrow‐band noise, the single‐cycle grating was detected with approximately 0·6 log units less contrast than the many‐cycle grating. On the other hand when both broad‐band and narrow‐band noise were present, there was no measurable difference in the detectability of the two types of grating.3. The results are interpreted as supporting the hypothesis of Campbell & Robson (1968) that spatially varying luminance patterns are processed by mechanisms selectively sensitive to limited ranges of spatial frequencies.