bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium currents in mammalian muscle
Authors: Adrian R. H. , Marshall M. W. 
Published: December 2014

1. A method is described which allows the approximate computation of membrane current from measurements with three electrodes in the mid‐region of a muscle fibre.2. Measurements of inward sodium current in frog muscle are compared with the results of previous clamping studies to test the validity of the new method.3. Sodium current in rat muscle (extensor digitorum longus) is in general similar to sodium current in frog muscle. Two differences in detail have been found between sodium current in rat and frog muscle: (a) at the same temperature (in the range 0‐20° C) inactivation is slower in the rat than in the frog; (b) in rat the steady‐state activation is shifted negatively on the voltage axis by some 10‐15 mV.4. Delayed outward current and charge movement (Schneider & Chandler, 1973) are present in rat muscle.5. Rat muscle fibres are more resistant than frog muscle fibres to the action of tetrodotoxin. Inward current is still detectable in rat muscle at 100 n
M tetrodotoxin. We found no evidence to suggest the existence in rat muscle of two kinds of sodium channel, one sensitive and one less sensitive to tetrodotoxin.
Laminar differences in receptive field properties of cells in cat primary visual cortex
Authors: Gilbert Charles D. 
Published: December 2014

1. Cells in area 17 of the cat visual cortex were studied with a view towards correlating receptive field properties with layering. A number of receptive field parameters were measured for all units, and nearly every unit was marked with a microlesion to determine accurately the layer in which it was found.2. Cells were defined as simple or complex by mapping with stationary stimuli, using the criteria of Hubel & Wiesel (1962). Complex cells fell into two groups: those that showed summation for increased slit length (standard complex) and those that did not (special complex).3. The simple cells were located in the deep part of layer 3, in layer 4, and in layer 6. This corresponds to the distribution of afferents from the dorsal layers of the lateral geniculate nucleus. In these cortical layers the simple cells differed primarily with respect to their receptive field size, cells in layer 4 having the smallest, layer 3 intermediate, and layer 6 the largest fields. Layer 4 was the only layer in which simple cells showed end‐inhibition (a reduction in response to slits extending beyond the excitatory portion of the receptive field).4. The standard complex cells were found in all layers, but were quite scarce in layer 4. As with the simple cells, field size varied with layer: in layer 2+3 they had small to intermediate field sizes, in layer 5 intermediate, and in layer 6 very large. Layer 6 cells showed summation for slits of increased length up to very large values, and responded best when the slits were centred in the receptive field.The only standard complex cells that showed end‐inhibition were those in layer 2+3, and these were similar to the layer 4 simple cells in terms of proportion of end‐inhibited units and degree of end‐inhibition.5. The special complex cells, originally described by Palmer & Rosenquist (1974), were found in two tiers: the upper one at the layer 3/layer 4 border and the lower one in layer 5. They were different from the standard complex cells in having a high spontaneous activity, high velocity preference, and large fields which were similar in size (at a given eccentricity) from one cell to the next. Many showed reduced response to slits of increasing length, even for slits that did not extend beyond the borders of the responsive region.6. Cells in layer 6 (the origin of the corticogeniculate projection) were antidromically activated from the lateral geniculate nucleus. The antidromically activated units included both simple and complex cells, and they had the long receptive fields characteristic of the overall population of cells in layer 6.7. The results showed that there are different types of simple and complex cells, and that cells in different layers have different properties. Taken together with their differences in site of projection, this demonstrates that the anatomical lamination pattern is reflected in functional differences between cells in different layers.
Properties of vestibular neurones projecting to neck segments of the cat spinal cord*
Authors: Rapoport S. , Susswein A. , Uchino Y. , Wilson V. J. 
Published: December 2014

1. Vestibular neurones projecting to the upper cervical grey matter (vestibulocollic neurones) were identified by localized microstimulation in the C3 segment of the cat spinal cord.2. The neurones were found in the lateral (Deiters'), medial and descending nuclei bilaterally and projected to the spinal cord in the lateral and medial vestibulospinal tracts (LVST and MVST). Ipsilateral axons of Deiters' neurones were mostly in the LVST, axons of medial and descending neurones in the MVST; a few Deiters' neurones had axons in the MVST; some descending neurones had axons in the LVST. Most axons of contralateral neurones were in the MVST.3. The axons of 62% of ipsilateral vestibulocollic Deiters' neurones not only gave off a collateral to C3, but also extended as far as the cervical enlargement (‘branching’); some of these neurones projected as far as the upper thoracic cord, almost none to the lumbar cord. Ipsilateral descending nucleus neurones branch in the same fashion, but there is no branching in the relatively small medial nucleus population.4. A large majority of vestibulocollic neurones receive monosynaptic excitation from the ipsilateral labyrinth and a number are inhibited by stimulation of the contralateral labyrinth (commissural inhibition). It is possible that commissural inhibition acts on a broad population of vestibular neurones involved in the control of eye, head and trunk movement.5. Vestibulocollic neurones do not make up a homogeneous population acting only on the neck. Instead it is likely that subpopulations, for example branching and non‐branching neurones, have different functions.
The effect of internal and external 4‐aminopyridine on the potassium currents in intracellularly perfused squid giant axons
Authors: Meves H. , Pichon Y. 
Published: December 2014

1. The effect of 4‐aminopyridine (4‐AP) on the K outward and inward currents in perfused giant axons of Loligo forbesi has been studied with the voltage‐clamp technique.2. Small internal or external 4‐AP concentrations (10‐100 μ
M) considerably delay the rise of the K outward current. Repetitive pulsing with a pulse interval of 0·1‐5 sec leads to a faster rise of the K current; in 10 μ
M 4‐AP a small effect is visible even with a pulse interval of 60 sec.3. The phenomenon has been studied quantitatively by using a prepulse of varying height and duration, followed after 5 sec by a constant test pulse. The effect of changing the holding potential has been investigated.4. The effect of repetitive pulsing disappears in higher 4‐AP concentrations; 1‐10 m
M 4‐AP markedly reduce the size of the K outward current; the blocking effect is less pronounced for large depolarizing pulses than for small.5. In K‐rich sea water 4‐AP reduces both the K outward current and the K inward current; the blocking effect on the K outward current is smaller than in K‐free sea water.6. The K outward current in fibres treated with 10 μ
M 4‐AP and immersed in K‐rich sea water is increased and accelerated by repetitive depolarizing pulses. The effect of repetitive pulsing is not dependent on the size of the K outward current (which can be increased by removing K inactivation).7. The effect of repetitive pulsing and the voltage dependence of the 4‐AP block can be explained by the hypothesis that 4‐AP molecules are displaced from their blocking sites during the pulse and slowly rebound afterwards. Removal of the 4‐AP block by a depolarizing pulse seems to be a direct effect of the potential during the pulse and not related to K current.
Pancreatic acinar cells: localization of acetylcholine receptors and the importance of chloride and calcium for acetylcholine‐evoked depolarization
Authors: Iwatsuki N. , Petersen O. H. 
Published: December 2014

1. Intracellular micro‐electrode recordings of acinar cell membrane potential and resistance were made from the mouse pancreas superfused in vitro. The acinar cells under investigation were stimulated by micro‐iontophoretic ACh application from an extracellular AChCl‐filled micro‐electrode.2. Passing short‐lasting ejecting current pulses through the AChCl‐electrode caused acinar cell depolarization when the electrode was in an extracellular position not far (< 50 μm) from an acinus impaled by a KCl micro‐electrode. After insertion of the AChCl electrode into a neighbouring acinar cell, electrically coupled to the acinar cell already impaled by the KCl‐electrode, ejecting ACh current pulses only affected the membrane potential in a direct electrical manner whereas there was no sign of an effect of ACh on the membrane potential.3. Replacing extracellular chloride by sulphate caused a marked increase in the amplitude of the ACh‐evoked depolarization. If the membrane potential was recorded with a KCl electrode ACh continued to evoke very large depolarizations even after more than 1 hr exposure to Cl‐free solution. If the membrane potential was recorded with a K‐citrate electrode the effect of Cl‐removal was only transient. Removal of Na+ during exposure to Cl‐free solution reduced the amplitude of the ACh‐evoked depolarization somewhat. Readmission of Cl after more than 1 hr of Cl deprivation caused an immediate reversal of the ACh effect into a hyperpolarization.4. Removal of extracellular Ca2+ caused a marked reduction in the amplitude of small depolarizations evoked by just suprathreshold doses of ACh, whereas there was very little effect on larger depolarizations evoked by maximal or supramaximal ACh ejections. The effect of Ca removal was fully reversible. Addition of Mn after Ca‐deprivation was as efficient as Ca in restoring normal electrophysiological responses to small doses of ACh.5. The acinar cell membrane seems only to be responsive to ACh added to the extracellular side and ACh probably causes an increase in membrane Cl permeability in addition to the previously described effects on Na and K permeability. Ca may be important in determining ACh receptor sensitivity.
Active Na—K transport and the rate of ouabain binding. The effect of insulin and other stimuli on skeletal muscle and adipocytes
Authors: Clausen Torben , Hansen Otto 
Published: December 2014

1. The effect of stimulation or inhibition of active Na—K transport on [3H]ouabain binding has been investigated in isolated soleus muscles and adipocytes.2. In rat soleus muscle, the ouabain‐sensitive component of 42K influx was stimulated by insulin (100 m‐u/ml.), adrenaline (6 × 10−6
M), and by pre‐incubation with veratrine (10−5
M) or in a K‐free buffer. In all of these instances, the rate of ouabain binding was increased by 41‐113%. Conversely, pre‐treatment with tetracaine (0·2 m
M) decreased the 42K‐influx and diminished the rate of [3H]ouabain binding by 36%.3. Neither insulin, adrenaline or tetracaine produced any detectable change in the total number of ouabain‐binding sites (as measured under equilibrium conditions) in rat soleus muscle.4. In mouse and guinea‐pig soleus muscle and in fat cells isolated from rats, insulin also increased the rate of [3H]ouabain binding without producing any significant change in the total number of ouabain‐binding sites.5. Both in soleus muscle and the epididymal fat pad of the rat, there was a linear correlation between 42K influx and the initial rate of [3H]ouabain binding.6. It is concluded that the rate of ouabain binding is determined significantly by the rate of active Na—K transport, but within the time intervals studied (4‐6 hr) stimulation or inhibition of the Na pump does not lead to any appreciable change in the total number of Na pumps. It seems unlikely that the stimulation of active Na—K transport by insulin or adrenaline is due to unmasking or de novo synthesis of Na pumps.
Developmental changes in the inward current of the action potential of Rohon‐Beard neurones
Authors: Baccaglini Paola I. , Spitzer Nicholas C. 
Published: December 2014

1. Rohon‐Beard cells in the spinal cord of Xenopus tadpoles have been studied in animals from early neural tube to free‐swimming larval stages. The onset and further development of electrical excitability of these neurones has been investigated in different ionic environments, to determine the ionic species carrying the inward current of the action potential.2. The cells appear inexcitable at early stages (Nieuwkoop & Faber stages 18‐20) and do not give action potentials to depolarizing current pulses.3. The action potential is first recorded at stage 20. (A) The inward current is carried by Ca2+ at stages 20‐25, since it is blocked by m
m quantitites of La3+, Co2+ or Mn2+ and is unaffected by removal of Na+ or the addition of tetrodotoxin (TTX). (B) The action potential is an elevated plateau of long duration (mean 190 msec at stages 20‐22). The duration decreases exponentially with repetitive stimulation. (C) The specific Ca2+ conductance (gCa) at the onset of the plateau of the action potential is 2·6 × 10−4 mho/cm2. Calculations show that a single action potential raises [Ca2+]1 by more than 100‐fold.4. At later times (stages 25‐40), the inward current of the action potential is carried by both Na+ and Ca2+: the action potential has two components, an initial spike which is blocked by removal of Na+ or addition of TTX, followed by a plateau which is blocked by La3+, Co2+ or Mn2+.5. Finally (stages 40‐51), the inward current is primarily carried by Na+, since the action potential is blocked only by removal of Na+ or addition of TTX, and the overshoot agrees with the prediction of the Nernst equation for a Na‐selective membrane. When the outward current channel is blocked and cells exposed to Na‐free solutions, 67% of cells at the latest stages studied were incapable of producing action potentials in which the inward current is carried by divalent cations.6. The duration of the action potential decreases from a maximum of about 1000 msec to about 1 msec during development. The maximum input resistance (Rin) decreases from ca. 1000 to 100 MΩ.7. The calcium action potential may play a role in the development of excitability and the growth of the neurones.
Brain stem stimulation and the acetylcholine‐evoked inhibition of neurones in the feline nucleus reticularis thalami
Authors: Dingledine Raymond , Kelly J. S. 
Published: December 2014

1. In cats anaesthetized with halothane and nitrous oxide, the responses to iontophoretically applied acetylcholine (ACh) and to high‐frequency stimulation of the mid‐brain reticular formation (MRF) were tested on spontaneously active neurones in the nucleus reticularis thalami and underlying ventrobasal complex.2. The initial response to MRF stimulation of 90% of the ACh‐inhibited neurones found in the region of the dorsolateral nucleus reticularis was an inhibition. Conversely, the initial response of 82% of the ACh‐excited neurones in the ventrobasal complex was an excitation. Neurones in the rostral pole of the nucleus reticularis were inhibited by both ACh and RMF stimulation.3. The mean latency (and
s.e. of mean) for the MRF‐evoked inhibition was 13·7 ± 3·2 ms (n = 42) and that for the MRF‐evoked excitation, 44.1 ± 4.2 ms (n = 35).4. The ACh‐evoked inhibitions were blocked by iontophoretic atropine, in doses that did not block amino acid‐evoked inhibition. In twenty‐four ACh‐inhibited neurones the effect of iontophoretic atropine was tested on MRF‐evoked inhibition. In all twenty‐four neurones atropine had no effect on the early phase of MRF‐evoked inhibition but weakly antagonized the late phase of inhibition in nine of fourteen neurones.5. Interspike‐interval histograms showed that the firing pattern of neurones in the nucleus reticularis was characterized by periods of prolonged, high‐frequency bursting. Both the ACh‐evoked inhibitions and the late phase of MRF‐evoked inhibitions were accompanied by an increased burst activity. In contrast, iontophoretic atropine tended to suppress burst activity.6. The possibility is discussed that electrical stimulation of the MRF activates an inhibitory cholinergic projection to the nucleus reticularis. Since neurones of the nucleus reticularis have been shown to inhibit thalamic relay cells, activation of this inhibitory pathway may play a role in MRF‐evoked facilitation of thalamo‐cortical relay transmission and the associated electrocortical desynchronization.
A long‐lasting potentiation of transmitter release related to an increase in transmitter stores in a sympathetic ganglion
Authors: Birks R. I. 
Published: December 2014

1. High frequency preganglionic nerve stimulation increases the acetylcholine (ACh) stores of the cat superior cervical ganglion. The increase reaches a maximum 20 min following 60 min conditioning stimulation at 20/s. The effect of this conditioning on ACh release in ganglia perfused with plasma and test stimulated at 4 or 5/s has been studied, and the relationship of ACh stores to ACh release in conditioned ganglia determined.2. The rate of ACh release in response to test stimulation at 5/s for 15 min, starting 20 min following conditioning, was 174% of the rate found in unconditioned ganglia. The ACh stores of the conditioned ganglia at the end of the test were calculated to be 173% of the control ganglion stores.3. When test stimulation at 4/s was started 5 min following conditioning, the rate of ACh release showed a variable pattern of increase and decrease over a 75 min period. The mean peak rate of release was about 150% of the control rate, and the duration of potentiation was about 75 min.4. When conditioned, unperfused ganglia were tested by stimulation at 4/s the ACh stores were found to increase and decrease in parallel with the increase and decrease in ACh release rates found in the perfusion experiments.5. It was found also that the magnitude of the increase in ACh stores and ACh release was related to the amount of ACh in the ganglionic stores at the onset of conditioning, being greater for the ganglia with the smaller initial stores.6. It is concluded that the potentiation of ACh release in ganglia conditioned in this way is directly related to the accompanying increase in ACh stores.7. The possible significance of alterations of ACh stores and ACh release as a mechanism of modulatory control of ganglionic transmission is discussed.
Quantitative aspects of responses in trigeminal relay neurones and interneurones following mechanical stimulation of sinus hairs and skin in the cat
Authors: Gottschaldt K.-M. , Young D. W. 
Published: December 2014

1. Stimulus‐response relationships in discharges of trigeminal relay‐ and interneurones were investigated in the barbiturate anaesthetized cat using controlled sinus hair or skin displacements.2. In comparison with discharges in slowly adapting primary afferent fibres the responses in all higher order neurones were considerably reduced in firing rate and often revealed modifications suggesting the interaction of mechanisms actively modulating the afferent input.3. In relay neurones with or without a tonic discharge component the ‘dynamic on’ response during a trapezoidal displacement of sinus hairs was found to be determined entirely or predominantly by the movement velocity and to be independent of the deflexion angle of a stimulus. In contrast, the static response in tonic relay neurones was determined by both the movement velocity and the displacement amplitude.4. Spatial summation of afferent input caused either only quantitative changes in the responses of relay neurones leaving the general discharge properties unaltered or caused both qualitative and quantitative changes in the responses.5. Interneurones consisted of two functional groups. In about 25% of them the responses were not or only slightly dependent on the intensity of the applied stimulus, often burstlike and of an all or nothing character. In the second group of interneurones the responses showed a quantitative dependence on the applied stimuli. In this group of interneurones responses often increased with the spatial extension of the peripheral stimulus revealing spatial summation of the afferent input.
The pH of brain extracellular fluid in the cat
Authors: Cragg Patricia , Patterson Lillian , Purves M. J. 
Published: December 2014

1. The blood supply to the medulla was determined by the injection of indian ink via the vertebral arteries. Virtually the whole medulla was supplied by penetrating vessels from the ventral surface. The highest density of small arterioles and venules was found close to the roots of XII and on the ventrolateral surface.2. The pH of extracellular fluid (pHe.c.f.) was measured with pH microelectrodes of tip size 1‐3 μm in cortex and medulla in seventeen cats, anaesthetized with pentobarbitone or a chloralose—urethane mixture. Parallel measurements were made of the pH of c.s.f. and plasma, the DC potential between plasma and brain and ventilation or phrenic nerve discharge.3. In the majority of tests under steady conditions, the pH of e.c.f. was found to be lower than that of c.s.f. by between 0·03 and 0·08 units. No systematic pH gradients could be found to a depth of 5 mm beneath the surface of either medulla or cortex.4. When plasma PCO2 was altered, pHe.c.f. changed with a latent period and speed of response related to the density of blood vessels. In vascular areas of the medulla and in the cortex, the latent period of 4 sec and the change of pHe.c.f. coincided with changes in ventilation. Changes in pHc.s.f. over the same areas were invariably slower.5. CO2 buffering capacities were in the order plasma > e.c.f. > c.s.f. Typical values were respectively, ‐2·2, ‐2·1 and ‐1·6.6. The pH of e.c.f. was unaffected by the intravenous injection of H+ and only slowly by the injection of HCO3‐. Only up to a depth of 1 mm beneath the surface was pHe.c.f. affected by superfusion of mock c.s.f. in the range 6·8‐8·0 units. This response had a latent period of 2‐3 min and was complete in 15 min.7. The pH of e.c.f. fell with hypoxia after a latent period of > 1 min and if all vasosensory nerves had been cut, pHe.c.f. was markedly affected by changes of blood pressure.8. These results indicate that even under steady conditions, the pH of e.c.f. and c.s.f. is not identical, that pHe.c.f. is more obviously affected by changes in Pa, CO2 than pHc.s.f. and that putative H+ sensors which drive respiratory neurones are likely to be similarly affected.