bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anomalous rectification in the metacerebral giant cells and its consequences for synaptic transmission
Authors: Kandel E. R. , Tauc L. 
Published: December 2014

1. In the central neurones that have so far been examined the passive electrical properties of the extrasynaptic membrane has been shown to be relatively constant in the subthreshold range. Consequently, excitatory synaptic potentials produced by chemical transmission tend to vary in amplitude with changes in membrane potential, decreasing with depolarization and increasing with hyperpolarization.2. In the two symmetrical giant cells of the ventral metacerebrum of the snail, the EPSPs failed to show the expected alterations in amplitude with changes in membrane potential. Near the resting level the EPSP increased slightly with membrane depolarization and decreased slightly with hyperpolarization.3. These paradoxical results were not attributable to a change in transmitter release since similar results were obtained when ACh, the putative transmitter, was released iontophoretically on to the cell membrane by means of an extracellular pipette.4. Measurement of the current—voltage relation of the extrasynaptic membrane revealed two types of rectifying conductance changes. The first, an increase in conductance with depolarization, was turned on at a depolarization of about 15 mV. Its conductance change was similar to the delayed rectification familiar from studies of peripheral nerve and muscle. The second occurred on either side of the resting level, from about 15 mV hyperpolarization to about 10 mV depolarization, and manifested itself as a decrease in conductance with depolarization and an increase with hyperpolarization. By analogy to a similar phenomenon known to occur in skeletal muscle this second rectification has been termed anomalous rectification.5. The average resistance at 25 mV hyperpolarization was 2·3 × 106 Ω, while at 10 mV depolarization it was 2·1 × 107 Ω, yielding an average rectification ratio of 10 for the anomalous conductance change.6. The anomalous rectifying conductance seems to account for the paradoxical behaviour of the EPSP and ACh response to changes in membrane potential. Moreover, the finding that the sharpest change in the anomalous rectification curve occurred on either side of the resting level suggests that this rectification is functionally important as a postsynaptic determinant of synaptic efficacy. Several additional lines of evidence in support of this suggestion have been obtained.
The composition of human saliva secreted in response to a gustatory stimulus and to pilocarpine
Authors: Dawes C. 
Published: December 2014

1. The composition of human saliva secreted in response to sour lemon drops (
S.L.D.), and pilocarpine, was studied.2. At a given flow rate, pilocarpine‐stimulated submandibular and parotid saliva contained less sodium and potassium and an equivalent amount of inorganic phosphate, and parotid saliva also contained more calcium and protein than did the corresponding types of
S.L.D.‐stimulated saliva.3. Prolonged
S.L.D. stimulation did not cause a depletion in the protein concentration of either parotid or submandibular saliva and neither this procedure nor pilocarpine stimulation altered the proportions of the different proteins secreted.4. Pilocarpine was judged to be an inadequate substitute for more physiological, gustatory stimuli.
The effect of inhibitors on intestinal transfer of glucose and fluid
Authors: Detheridge Joan F. , Matthews J. , Smyth D. H. 
Published: December 2014

1. The effect of various experimental conditions has been studied on the transfer of hexoses and fluid by everted sacs of rat small intestine.2. The existence of glucose‐dependent and glucose‐independent mechanisms has been confirmed; the energy for the former comes from the citric acid cycle, and for the latter from either the glycolytic or pentose cycle.3. The energy for glucose transfer against a concentration gradient can come from metabolism of glucose by some route other than the citric acid cycle, or it may come from the citric acid cycle.4. Two‐stage transfer of glucose is discussed as a possible explanation of the results.
A study of the inhibitory action of γ‐aminobutyric acid on neuromuscular transmission in the crayfish
Authors: Takeuchi A. , Takeuchi Noriko 
Published: December 2014

1. The effect of γ‐aminobutyric acid (GABA) on the neuromuscular junction of the crayfish (Cambarus clarkii) was investigated. The drug was applied iontophoretically to a junction and the potential changes were recorded intracellularly as well as extracellularly with micro‐electrodes.2. The amplitude of the potential produced by iontophoretically applied
L‐glutamate was decreased by simultaneous application of GABA to the same junctional area. When the membrane potential was clamped at the resting level the clamping current for the
L‐glutamate injection was not changed by GABA application, indicating that there is no appreciable competition between
L‐glutamate and GABA for the glutamate‐sensitive receptor.3. The excitatory nerve was stimulated repetitively and the excitatory junctional potentials (e.j.p.s) were recorded extracellularly with a micro‐electrode placed on the surface of the muscle. The average size of the extracellular e.j.p.s was reduced by the application of GABA.4. The number of quanta released per impulse calculated from the extracellular e.j.p.s was decreased during the application of GABA, while the quantum size remained unchanged.5. The size of the excitatory presynaptic nerve spike was decreased by the application of GABA. However, no appreciable change was observed in the inhibitory nerve spike.6. These results indicate that in addition to its post‐synaptic action GABA acts on the excitatory presynaptic nerve terminal and reduces the release of the transmitter.
On the permeability of the presynaptic terminal of the crayfish neuromuscular junction during synaptic inhibition and the action of γ‐aminobutyric acid
Authors: Takeuchi A. , Takeuchi Noriko 
Published: December 2014

1. The contribution of chloride to presynaptic inhibition of the crayfish neuromuscular junction during the action of γ‐aminobutyric acid (GABA) and the inhibitory transmitter was investigated. Chloride in van Harreveld's solution was replaced with propionate, acetate, methylsulphate or glycerophosphate and electrical changes were recorded intracellularly and extracellularly with micro‐electrodes.2. When the preparation was soaked in Cl‐deficient solutions, the quantum content of the excitatory junctional potentials (e.j.p.s), calculated from the number of failures, was increased.3. The presynaptic inhibitory action of GABA was reduced or almost absent when the preparation was soaked in Cl‐deficient solution. In Cl‐deficient solution the stimulation of the inhibitory axon showed little or no inhibitory action on e.j.p.s.4. If GABA was applied shortly after the outside solution was changed to the Cl‐deficient one, the frequency of the spontaneous e.j.p.s was increased transiently.5. It is suggested that GABA or the inhibitory transmitter act on the presynaptic excitatory terminal and predominantly increase its permeability to chloride.
Electrical responses of smooth muscle to external stimulation in hypertonic solution
Authors: Tomita T. 
Published: December 2014

1. The electrical responses of single smooth muscle cells of the guinea‐pig taenia coli to external stimulation were studied in two times hypertonic solution and compared with the responses to intracellular stimulation.2. Exposure to Krebs solution made two times hypertonic by adding sucrose abolished the mechanical movement and stopped the spontaneous electrical activity. The electrical response to stimulation was essentially similar to that in physiological solution.3. When the tissue was placed between stimulating electrodes, the cells near the cathode were depolarized and produced spikes, while the cells near the anode were hyperpolarized and produced small spikes only with weak stimuli. The cells near the centre were not polarized but produced spikes with a frequency pattern similar to that near the cathode.4. When both stimulating electrodes were put close together at one end of the tissue, the intracellularly recorded extrapolar polarization changed its polarity at 1–2 mm distance from the stimulating electrode. When an insulating partition was placed between the stimulating and recording site, the reversed polarity was no longer observed and the electrotonic potential spread decayed roughly exponentially with distance from the stimulating electrode. The time course of the electrotonic potential was similar to that predicted from the cable equation applied to nerve. The space constant was 1·68 ± 0·08 mm (
S.E. of mean) and the time constant was 60‐100 msec. The cable properties may be explained by assuming that many fibres, connected in series and in parallel, are aggregated as functional units.5. The strength—duration curve was a simple hyperbola and the chronaxie was about 20 msec. The relation between extracellularly applied current and intracellularly recorded potential showed that membrane resistance decreased with depolarization and slightly increased with hyperpolarization. The spike was propagated in both directions at the same speed as in physiological solution (7·3 ± 0·7 cm/sec).6. Long anodal current often produced electrical activity of low amplitude which seemed to be due to the spike activity near the cathode, because the same frequency modulation was seen in both activities, and external hyperpolarization reduced the size of the propagated spike. Cessation of a strong and long anodal current was followed by slow depolarization, about 1 sec in duration and up to 10 mV in amplitude, which sometimes triggered a spike.7. The difference between responses to intracellular and to external stimulation may be explained by assuming that different parts of the cell membrane have different electrical properties. They may be: A, areas of close apposition between cells; B, areas capable of generating the slow component; C, an area capable of producing the spike, but less excitable.
The flicker fusion frequency of the blue‐sensitive mechanism of colour vision
Authors: Brindley G. S. , Du Croz J. J. , Rushton W. A. H. 
Published: December 2014

1. The flicker fusion frequency for blue stimuli on zero background increases steadily with increasing luminance up to 50 c/s, but if a strong yellow background is added it increases steadily only to about 18 c/s, and then remains nearly independent of luminance over a range of a factor of 20.2. It is argued that the maximum flicker fusion frequency is about three times lower for the blue‐sensitive mechanism of colour vision than for the red‐ or green‐sensitive.
The thalamic relay and cortical projection of Group I muscle afferents from the forelimb of the cat
Authors: Andersson S. A. , Landgren S. , Wolsk D. 
Published: December 2014

1. Stimulation of Group I muscle afferents in contralateral forelimb nerves evoked a response in nucleus ventralis posterolateralis (VPL) in the thalamus of the cat. This response was located in the rostral two‐thirds of VPL in a narrow zone near the dorsomedial border of the nucleus.2. Group I afferents in nerves from more than one of the muscles in the contralateral forelimb often excited the same thalamic relay cell. In addition these cells were often discharged by skin afferents from the contralateral forelimb. They were not affected by electrical stimulation of the dorsal column‐lemniscal or the spino‐cervico‐lemniscal paths from the contralateral hind limb.3. In experiments with peripheral conduction paths of similar length, the latency of the thalamic focal potential evoked by stimulation of Group I muscle afferents in the nerve to m. extensor carpi radialis was 3·8
S.E. ± 0·1 msec, and that of the focal potential evoked by skin afferents (n. radialis superficialis) in the centromedial part of VPL was 4·3 ± 0·1 msec.4. The majority of the thalamic neurones discharged by Group I muscle afferents responded with a latency shorter than 1 msec to electrical stimulation of the cerebral cortex in the region of the post‐cruciate dimple. A considerable number of the thalamic Group I relay cells were also discharged with a similar short latency from another cortical focus located on either side of the anterior suprasylvian sulcus near the S II hind limb areas. These responses were considered to be antidromic in nature, and the findings were interpreted as indicating two separate cortical projection areas for the Group I path. The second projection area was assumed to be located in the cortical fold formed by the anterior suprasylvian sulcus.5. Cortical stimulation also excited the thalamic Group I relay cells trans‐synaptically. Trans‐synaptic excitation with short (1‐2 msec) and longer (2‐7 msec) latency was observed. The cortical focus near the S II area was particularly potent in evoking trans‐synaptic excitation in the thalamic region where the Group I relays were located.
Analysis of sodium and potassium conductances in the procaine end‐plate potential
Authors: Maeno Takashi 
Published: December 2014

1. The effect of procaine on neuromuscular transmission was studied on the sartorius muscle of the frog, Rana pipiens, with intracellular microelectrodes.2. Mean quantal content of the e.p.p. in high Mg Ringer was little affected by procaine.3. The short circuit effect of the e.p.p. on the action potential, which was an indication of change in potassium conductance (ΔgK) during the e.p.p., was investigated on the muscle fibre immobilized in hypertonic Ringer. It was found that procaine had little effect on ΔgK.4. The equilibrium potential of the e.p.p. (Ee.p.p.) was measured in hypertonic Ringer. Ee.p.p. was 12 mV in control experiment and was decreased to 3·1 mV in 10−4 procaine. The ratio ΔgNa/ΔgK was calculated to be 2·75 in control and 2·11 in 10−4 procaine.5. E.p.p.s were recorded extracellularly to study changes in the time course of ΔgNa in procaine. Procaine reduced the peak magnitude of ΔgNa; following the peak, ΔgNa fell quickly to a lower level, which decayed much more slowly.6. An end‐plate model with separate sodium and potassium pathways is proposed to explain the procaine e.p.p. Procaine is assumed to affect the time course of ΔgNa.7. E.p.p.s simulated from the proposed end‐plate model with theoretical ΔgNa and ΔgK agreed satisfactorily with actual procaine e.p.p.
Circulatory responses to simulated gravitational shifts of blood in man induced by exposure of the body below the iliac crests to sub‐atmospheric pressure
Authors: Brown Ellen , Goei J. S. , Greenfield A. D. M. , Plassaras G. C. 
Published: December 2014

1. Exposure of the body from iliac crests to feet of a horizontal subject to a pressure 70 mm Hg below atmospheric causes a displacement of about 10 g of blood/kg total body weight from the upper to the lower part of the body. Much of this blood is returned very rapidly at the end of suction.2. During suction, the changes in the circulation resemble those during a foot‐down tilt. After suction, the changes resemble to some extent those following the Valsalva manoeuvre.3. The overshoot of forearm blood flow following suction is caused by variations in the activity of adrenergic vasoconstrictor nerves. The receptors for this reflex have not been identified, but their stimulation depends upon a rapid and large return of blood to the central circulation.
Application of the sucrose‐gap method to determine the ionic basis of the membrane potential of smooth muscle
Authors: Bennett M. R. , Burnstock G. 
Published: December 2014

1. A study has been made of the ionic basis of the smooth muscle membrane potential by changing the ionic environment of the ureter and recording the resultant potential changes with the sucrose gap. The relation of these potential changes to the membrane potential of individual cells has also been studied.2. It is shown that if the ionic environment of all the cells in the tissue is uniformly changed, then the potential change recorded by the sucrose gap is proportional to the magnitude of the short circuit factor, the liquid junction potential change at the sucrose‐test solution interface, and the amplitude of the membrane potential change of a single cell.3. A simple method is described for determining the steady value of the short circuiting factor, and the liquid junction potential changes, so that the recorded potentials can be corrected to give membrane potentials.4. The action of isotonic potassium sulphate and isotonic potassium chloride on the membrane potentials of the ureter smooth muscle cells is described.5. When the extracellular potassium concentration is changed reciprocally with the extracellular chloride concentration in order to maintain these ions in a Donnan equilibrium across the muscle cell membrane, the membrane potential is found to decrease by 53 mV for a 10‐fold change in external potassium concentration, for concentrations above 10 m
M.6. It is concluded that above an external potassium concentration of 10 m
M the membrane potential of ureteral smooth muscle cells obeys the prediction of the Nernst equation for a potassium electrode.
Central pathways of some autonomic reflex discharges
Authors: Coote J. H. , Downman C. B. B. 
Published: December 2014

1. Electrical stimulation of spinal sensory nerves evoked discharges in inferior cardiac and renal nerves. In the anaesthetized cat both an early and a late response could be recorded in each nerve.2. For any one afferent input the central delay of the late cardiac nerve response was significantly less than that of the late renal nerve response. The central delay of the early responses was similar for both nerves. In the spinal cat only the early response was present.3. Cooling the floor of the 4th ventricle abolished the late responses in renal nerves, but left reflex volleys in white rami and intercostal nerves unchanged.4. Stimulation in the brain stem evoked responses in both cardiac and renal nerves which had a shorter latency than the reflexes evoked in these nerves by stimulating dorsal roots.5. The late responses could be abolished by lesions in the cervical spinal cord.6. Such evidence led to the conclusion that there are two pathways for reflex discharge into inferior cardiac and renal nerves, one involving a supraspinal relay and the other confined to the spinal cord.
An inhibitory process in the cerebral cortex
Authors: Krnjević K. , Randić Mirjana , Straughan D. W. 
Published: December 2014

1. In cats, rabbits and monkeys, single cortical shocks can reduce the excitability of cortical neurones for 100‐300 msec; the inhibitory effect is readily demonstrated, even in previously quiescent cells, against a background of activity evoked with small amounts of
L‐glutamate, released from an extracellular recording micropipette by iontophoresis.2. Other forms of cortical activity are also inhibited in a similar way by direct or indirect cortical stimulation; they include single unit discharges produced by iontophoretic applications of ACh or by a cathodal current, spontaneous discharges, and slow wave activity, both spontaneous and evoked.3. Most stimuli which elicit cortical activity also evoke some inhibition in the cortex, for instance, transcallosal volleys, and thalamic or peripheral shocks. In each case, a characteristic, prolonged depression is produced by single shocks.4. The most effective stimuli are direct cortical shocks, especially when applied within the cortex, below a depth of 0·6 mm; surface cathodal shocks are more effective than anodal shocks. These stimuli do not first excite the cells which are inhibited and they are not strong enough to cause appreciable local injury.5. Because of its long duration, the inhibition is often readily maintained by repetitive stimulation at frequencies of 5‐7/sec. A cumulative effect leads to a further silent period after the end of stimulation; this increases with the strength, frequency and duration of the tetanus, so that after stimulation at 50‐100/sec, the silent period may last for over 1 min. During this time, a stronger depolarizing stimulus can initiate firing.6. The inhibitory effect is often preceded and followed by phases of increased excitability; these may also show cumulative enhancement during repetitive stimulation, and a high frequency tetanus often leads to a short after‐discharge, which is then followed by a long silent period, as above. Comparable changes take place in rabbits during spreading depression.7. The inhibitory effect of a direct shock can spread over an area covering 1 cm of cortical surface, affecting the cells through all cortical layers; but the spread is uneven in different directions, being particularly poor under most sulci.8. This type of inhibition can be elicited in all areas of the neocortex, and it is evident in kittens within a week of birth.9. Antidromic pyramidal stimulation is very much less effective in evoking inhibition of Betz cells, and other cortical neurones, than direct cortical stimulation; the inhibition by direct shocks is therefore not likely to be mediated through pyramidal excitation.
Nature of a cortical inhibitory process
Authors: Krnjević K. , Randić Mirjana , Straughan D. W. 
Published: December 2014

1. Since the inhibitory effect of direct or indirect cortical stimulation on cortical units can be overcome by excitation with even more
L‐glutamate, it is not likely to be due to an excessive depolarization.2. Further evidence that surface stimulation has a hyperpolarizing action on cortical cells was obtained by intracellular recording from over 120 pericruciate cells. Inhibitory post‐synaptic potentials (IPSPs) are seen in most cells, which are comparable in threshold and duration with the inhibitory effect observed extracellularly. The IPSPs are usually not preceded by a discharge of the same cells.3. The extracellular slow wave corresponding to the inhibitory effect varies considerably with different preparations and different depths within the cortex. A predominantly positive wave is only seen occasionally. In general, the relevant wave recorded deep in the cortex tends to be mainly negative.4. This negative slow wave can be much potentiated by tetanic stimulation, or, especially, by a large local release of
L‐glutamate; the last procedure is most effective either very near the surface, or below a depth of 1·0 mm. These observations suggest that inhibitory synapses occur more profusely in the superficial half of the grey matter.5. Unlike
L‐glutamate, GABA tends to depress the ‘inhibitory’ slow wave.6. The inhibitory effect must be produced by intracortical neurones, since it is fully preserved in isolated cortical slabs. In both acute and chronic slabs, the inhibition is particularly well marked and long lasting, partly because spontaneous activity and the usual post‐inhibitory rebound of excitability are absent.7. The intracortical pathways responsible for the spread of inhibition cannot be situated mainly in the superficial layers, as they are not readily blocked by surface cooling or the application of local anaesthetics.8. One can record unit discharges immediately after a surface shock. Some of these discharges could be from inhibitory interneurones, but they do not last more than 10‐20 msec.9. We conclude from the observations described in this and a previous paper (Krnjević, Randić & Straughan, 1966a) that a widespread system of intracortical interneurones can be activated by direct or indirect stimulation of the cortex; these interneurones have a powerful and prolonged inhibitory action on most cortical cells.10. The identity and distribution of the postulated inhibitory interneurones is discussed in the light of some relevant morphological evidence.