bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the nature of histamine‐mediated slow hyperpolarizing synaptic potentials in identified molluscan neurones
Authors: McCaman R. E. , Weinreich D. 
Published: December 2014

1. Standard intracellular stimulating and recording techniques were used to test the correspondence between monosynaptic post‐synaptic potentials (p.s.p.s) evoked by histamine‐containing C‐2 neurones and responses to focally applied histamine recorded from two classes of identified post‐synaptic neurones in the cerebral ganglion of Aplysia californica.2. Two types of p.s.p.s were examined: (1) a monophasic slow hyperpolarizing potential (Isp.s.p.) lasting 1‐2 sec; and (2) a biphasic p.s.p. consisting of a fast depolarizing component <0·5 sec in duration (Efp.s.p.) plus a slow hyperpolarizing potential (Isp.s.p.) designated the EfIsp.s.p.3. Ionophoretic or pressure applied histamine mimicked both p.s.p.s and produced conductance increases in the post‐synaptic neurones similar to those associated with the evoked p.s.p.s.4. The reversal potentials (Erev) for the Isp.s.p. and EfIsp.s.p., estimated by extrapolation, were ‐85±5·3, ‐35±5·5, and ‐83±8·1 mV (mean±S.D.), respectively. The Isp.s.p.s were produced by an increase in potassium conductance because their Erevs were shifted about 16 mV by doubling or halving the concentration of extracellular potassium and they could be eliminated by cooling or by intracellular injection of TEA ions.5. The average Erev values for the slow hyperpolarizing histamine responses were similar to those for the Isp.s.p.s; about ‐83 and ‐86 mV in neurones receiving the monophasic Isp.s.p.s and biphasic EfIsp.s.p., respectively.6. Cimetidine, an antihistamine drug that selectively blocks histamine receptors associated with potassium conductances in Aplysia, reversibly abolished the Isp.s.p.s and slow hyperpolarizing responses to focally applied histamine. In similar concentrations, cimetidine had no discernible effects on the Efp.s.p. and depolarizing response to histamine or on several different types of p.s.p.s mediated by the C‐2 neurones.7. It is proposed that the Isp.s.p.s are mediated by histamine released from the C‐2 neurones.
Control of evaporative heat loss during changes in plasma osmolality in the cat
Authors: Baker M. A. , Doris P. A. 
Published: December 2014

1. The effects of intravenous infusion of hypertonic saline and distilled water into normally hydrated and dehydrated cats have been examined at both high and neutral ambient temperatures.2. In hydrated cats measurements of body temperature (Tb) and evaporative heat loss (e.h.l.) show that infusion of 30% saline (1·5 ml./kg) at an ambient temperature of 38 °C, lowers e.h.l. by an average of 0·21 W/kg (P < 0·001) and elevates Tb by 0·43 °C (P < 0·01).3. At 25 °C alterations in these two parameters were in the same direction, though not statistically different from pre‐infusion levels (P > 0·05).4. Infusion of distilled water (15 ml./kg) into dehydrated animals produced significant increases in e.h.l. (+0·35 W/kg, P < 0·001) and reductions in Tb (‐0·45°C, P < 0·001) at 38 °C. No significant effects were observed at 25 °C.5. Infusion of water into normally hydrated animals at 38 °C also significantly increased e.h.l. (+0·13 W/kg, P < 0·05) and insignificantly lowered Tb (‐0·03 °C, P > 0·05).6. Local heating of the preoptic hypothalamic area in four animals indicated that hypertonic saline infusion into normally hydrated animals caused a reduction in the slope and displacement to the right of the relationship between hypothalamic temperature and e.h.l.7. Conversely, water infusion into dehydrated animals increased the slope and shifted this relationship to the left.8. These experiments provide evidence for an osmotic interaction in body temperature regulation which acts to alter the responsiveness of the hypothalamus to increasing temperature. This osmotic component may be an important factor in the alterations in thermoregulation seen in dehydrated animals.
Effects of calcium and strontium in the process of acetylcholine release from motor nerve endings
Authors: Mellow A. M. , Perry B. D. , Silinsky E. M. 
Published: December 2014

1. The effects of Ca and Sr ions on synchronous acetyleholine (ACh) secretion (the impulsive, physiologically functional form of secretion which produces an end‐plate potential in response to a single nerve impulse) and on asynchronous ACh secretion (the delayed, residual increase in miniature end‐plate potential frequency evoked by repetitive nerve impulses or by accumulation of intracellular divalent cations) were studied at frog neuromuscular junctions.2. In a comparison of their extracellular effects, Ca was far more effective than Sr in supporting synchronous ACh secretion but less effective than Sr in mediating asynchronous release evoked by repetitive nerve impulses.3. In studies of their intracellular effects, Sr and Ca were delivered to the nerve terminal cytoplasm using liposomes as a vehicle. Ca‐containing liposomes, although producing effects on asynchronous ACh secretion that were indistinguishable from those of equimolar Sr‐containing liposomes, were more effective than Sr‐containing liposomes in increasing synchronous release.4. Extracellular Ca behaved as a potent competitve inhibitor of asynchronous, neurally evoked release mediated by Sr. In contrast, intracellular Ca (i.e. liposomal Ca), whilst increasing synchronous ACh release, failed to antagonize evoked asynchronous release.5. The results demonstrate that synchronous and asynchronous secretion have different sensitivities to alterations in intracellular divalent cation concentrations. It is suggested that selectivity for Ca over Sr may occur at intraterminal sites responsible for synchronous ACh secretion but not at sites responsible for asynchronous ACh release. Furthermore, Ca appears to bind with high affinity as an antagonist at the external surface of the nerve ending. These results are discussed in conjunction with current theories of depolarization—secretion coupling.
The pH oscillations in arterial blood during exercise; a potential signal for the ventilatory response in the dog
Authors: Cross Brenda A. , Davey A. , Guz A. , Katona P. G. , Maclean M. , Murphy K. , Semple S. J. G. , Stidwill R. 
Published: December 2014

1. The effect of electrically induced ‘exercise’ on the respiratory oscillation of arterial pH was studied in chloralose‐anaesthetized dogs with spinal cord transection at T8/9 (dermatome level T6/7).2. Respiratory oscillations of arterial pH (presumed to be due to oscillations of arterial PCO2) were sensed with a fast‐responding electrode in one carotid artery. Breath‐by‐breath estimates of the maximum rate of change of pH of the downstroke of the pH oscillation (dpH/dt↓max) were obtained by differentiating the pH signal.3. Consistent with the findings of the previous paper (Cross et al. 1982), the ventilatory response to exercise could not be explained on the basis of sensitivity to CO2; the ΔV̇I/ΔPa, CO2 was significantly greater for ‘exercise’ than for CO2 inhalation.4. On average, the amplitude of the pH oscillations decreased during ‘exercise’. The change in the phase relationship (ϕ) between respiratory and pH cycles, although significant from the second breath onwards, was not thought to be responsible for the increased ventilation V̇I; the direction of the change was opposite to that previously found to increase V̇I.5. Inspiratory duration (ti), expiratory duration (te), V̇I and the dpH/dt↓max changed significantly by the third breath of ‘exercise’. A significantly linear relationship was obtained between te and dpH/dt↓max during the on‐transient (first ten breaths) of ‘exercise’. This relationship was maintained throughout ‘exercise’. V̇I and dpH/dt↓max were also linearly related during the on‐transient, although the same relationship did not hold true throughout ‘exercise’.6. The dpH/dt↓max was related to CO2 production (V̇CO2) lending support to the prediction that the slope of the downstroke of the pH oscillation is a function of V̇CO2.7. It was concluded that the dpH/dt↓max (dpCO2/dt↑max) is a potential humoral signal in ‘exercise’ and could account totally for the shortening of te. Since there was a late rise in V̇I (due to an increase in tidal volume VT) in the absence of a change in dpH/dt↓max, it was considered unlikely that the dpH/dt↓max was the only humoral signal present during ‘exercise’.
Effects of hypertonic solutions on quantal transmitter release at the crayfish neuromuscular junction
Authors: Niles Walter D. , Smith Dean O. 
Published: December 2014

1. The effects of a hypertonic bathing medium, containing either NaCl or melezitose, on the average number (m) and the time course of quantal release following an action potential were studied using focal extracellular recording methods at synaptic sites on the opener muscle of the crayfish leg.2. After the application of hypertonic saline, the rate of spontaneous quantal release increased but m decreased to a new level within 1 min; the extent of depression depended on the magnitude of the increase in tonicity until the osmolarity was 50% greater than the normal value of 0·43 osmol/l (Osm), but greater increases in tonicity exerted little further effect.3. The synaptic delays were increased and distributed over a longer range of time in hypertonic solutions; also, the latency between the first and second quantal releases in a multiple response to a single nerve impulse was also increased.4. Hypertonicity had no significant effect on the conduction velocity of the action potential, the independence of successive quantal releases in the same response, or the uniformity of the rise and fall of the probability of quanta release following an action potential, α(t).5. The time course of α(t) is prolonged in hypertonic solutions; this was manifested as an increase in the time constant of the exponential decline in α(t) from its peak value following the nerve impulse.5. When the potentiating agent 5‐hydroxytryptamine (5‐HT) was added to the hypertonic saline, m was increased, and the time course of α(t) was prolonged further than in the hypertonic solution alone; 5‐HT produced no change in the time course of α(t) when it was added to normal saline, although m was increased.6. It is concluded that in this preparation hypertonicity decreases the rate of release of each quantum from the nerve terminal following a nerve impulse.
Analysis of orientation bias in cat retina
Authors: Levick W. R. , Thibos L. N. 
Published: December 2014

1. Responses of cat retinal ganglion cells to a drifting sinusoidal grating stimulus were measured as a function of the grating orientation and spatial frequency.2. The response at fixed frequency and contrast varied with orientation in the manner of a cosine function. A new measure was introduced to quantify this orientation bias in the response domain on an absolute scale of 0‐100%. Under experimental conditions designed to maximize the effect, the mean bias for 250 cells was 16% and the range was 0‐46%. In 70% of cells there was significant bias.3. Orientation bias varied with spatial frequency and was maximal near the high‐frequency limit. The majority of biassed cells preferred the same orientation at high and low frequencies but in some cells a reversal occurred: the orientation which gave maximum response at high frequencies gave minimum response at low frequencies. The greatest variation of cut‐off frequency with orientation was ⅔ octave.4. Orientation bias was due to neural, not optical, factors. Nevertheless, the phenomenon could often be imitated by deliberately introduced optical astigmatism of up to 4 dioptres for brisk‐sustained units and over 10 dioptres for brisk‐transient units.5. The grating orientation preferred by cells varied systematically with position in the visual field. The central tendency was for the grating which yielded maximum response to lie parallel to the line joining the cell to the area centralis. This generalization failed for units within 2° of the centre of the area centralis.6. Analysis of orientation bias indicates a functional asymmetry of receptive fields such that the centre mechanism, and sometimes also the surround mechanism, is elongated along the line joining cell to area centralis.
The responses to somatic stimuli of deep spinothalamic tract cells in the lumbar spinal cord of the cat
Authors: Meyers D. E. R. , Snow P. J. 
Published: December 2014

1. The responses to natural somatic stimuli of thirty‐seven antidromically identified spinothalamic tract (s.t.t.) cells in Rexed's laminae VII and VIII of the lumbar spinal cord of the cat have been studied. A further twenty‐eight s.t.t. cells were identified antidromically.2. Cells were activated from sites in, or close to, one of the following locations: nucleus (n.) parafascicularis or n. centrum medianum, magnocellular part of the medial geniculate or the medial leminiscus, n. ventralis posterior medialis, n. lateralis posterior.3. The majority (84%) of s.t.t. cells showed spontaneous discharge at 1‐67 Hz.4. Somatic stimuli excited 81% of s.t.t. cells but gave rise to inhibition of spontaneous discharge in 54% of cells. Only 8·1% of cells gave only inhibitory responses while 35·1% gave only excitatory responses and 45·9% gave both inhibitory and excitatory responses. No response could be elicited in 10·8% of cells.5. The proportion of s.t.t. cells giving inhibitory and excitatory responses to hair movement, light touch or tap, innocuous pinch, noxious pinch, joint movement, twisting of and intense pressure on joints, flicking, palpation or deflexion of large muscles, skin cooling and warming and noxious heat are documented. Of these stimuli, only skin cooling and warming failed to produce a response in any cell.6. Many cells showed convergence from receptors in muscles, joint and skin although 29·7% responded exclusively to innocuous cutaneous stimuli.7. Convergence from receptors on wide, and sometimes quite separate, areas of the hind quarters was common but exclusively contralateral receptive fields were not found and for none of the above stimuli was the contralateral side more effective than the ipsilateral side.
The morphology of physiologically identified deep spinothalamic tract cells in the lumbar spinal cord of the cat
Authors: Meyers D. E. R. , Snow P. J. 
Published: December 2014

1. The morphology of eleven physiologically identified, deep, spinothalmic tract (s.t.t.) cells in the seventh lumbar segment of the cat were studied after being intracellularly injected with horseradish peroxidase (HRP).2. Four of these cells, prepared for combined light and electron microscopy, did not appear to be as well filled with HRP as the other cells which were prepared solely for the light microscope. In these four cells the axons were not stained and significantly fewer distal dendrites were stained.3. The axons of the other seven cells projected medially, crossed the mid line in the ventral white commissure and ascended in the contralateral ventral funiculus. No axon collaterals were found.4. The dendrites of eight cells could be divided into three groups. The first group projected laterally across lamina VII, usually passing through the ventrolateral portion of lamina VI before entering the lateral funiculus. The second group projected ventrally, ventromedially and ventrolaterally through the ventral parts of laminae VII and VIII and into the ipsilateral ventral funiculus. The third group projected towards the central canal, the ventral border of the dorsal columns and the dorsal parts of the ipsilateral ventral funiculus. This group usually branched profusely and projected into lamina X.5. Of the remaining three cells, one was located more deeply than any other cell, one was probably incompletely filled, and one was located more laterally. The first two cells had dendritic trees which bore strong similarities to the other eight cells described above.6. In all, 12·3‐37·5% of dendritic tips were found in the white matter of the ventral or lateral funiculi.7. Dendrites never entered the dorsal columns but they could often be traced to points very close to the dorsal columns before they turned abruptly and ran parallel to the grey‐white border.8. These data are discussed in relation to the excitatory and inhibitory responses of s.t.t. cells to somatic stimuli and the axonal projections of physiologically identified primary afferents and spinal interneurones.
Effect of fusimotor stimulation on Ia discharge during shortening of cat soleus muscle at different speeds
Authors: Appenteng K. , Prochazka A. , Proske U. , Wand P. 
Published: December 2014

1. In barbiturate‐anaesthetized cats, the L7 and S1 dorsal and ventral roots were dissected to isolate functionally single afferents identified as primary endings of soleus muscle spindles, and motor filaments which exerted a fusimotor action on the afferents with limited action on extrafusal muscle. Up to seven filaments, with an action on a given primary ending, could be isolated and each was classified as exerting either a predominantly dynamic or static action.2. Combined stimulation of these filaments, at rates up to 200 impulses/s could maintain afferent firing during muscle shortenings at speeds up to 200 mm/s.3. Fusimotor stimulation could also maintain afferent firing at a target frequency of 100 impulses/s during muscle shortenings up to 200 mm/s. The timing, in relation to the onset of shortening, and the rates of fusimotor stimulation were found to be critical in achieving the target frequency.4. Sinusoidal modulation of the frequency of fusimotor stimulation was used to study the conditions required to achieve constant afferent firing in the face of imposed sinusoidal length changes.5. For given depths of modulation, the phase advance of fusimotor stimulation needed to produce minimum modulation of afferent firing (best compensation) increased with increasing frequency of the sinusoids. The compensation deteriorated with an increase in the frequency of the sinusoids and a change in the mean muscle lengths, although in some cases it could be restored by adjustments to the depth of modulation of fusimotor rate. This suggests that for movements of varying speeds and amplitudes, settings which are appropriate for shortening at a given velocity and mean muscle length, do not apply if either of these two variables are altered.6. These findings demonstrate that the fusimotor system is potentially capable of eliciting constant afferent firing as envisaged in the ‘servo‐assistance’ hypothesis (Matthews, 1964, 1972; Stein, 1974). This, and the fact that constant afferent firing is not seen during normal unobstructed shortenings at velocities greater than 0·2 resting length/s (Prochazka, 1981), are used to argue that it is by choice rather than necessity that ‘servo‐assistance’ (as defined above) is not employed during normal movements. However, servo‐assistance of a different form (involving modulated spindle afferent feed‐back from both agonists and antagonists) remains a viable alternative.
Differences between foreign and original innervation of skeletal muscle in the frog
Authors: Sayers Helen , Tonge D. A. 
Published: December 2014

1. In order to investigate the characteristics of synapses formed by a foreign nerve in skeletal muscle of the frog, the hypoglossal nerve in Rana pipiens was implanted under the cutaneus pectoris (c.p.) muscle which was denervated 1 month later.2. Within 1 week of crushing the c.p. nerve, hypoglossal nerve fibres could be seen extending towards the denervated end‐plates and the muscle contracted in response to stimulation of the implanted nerve.3. The synapses formed by the foreign nerve differed from those of the original nerve in several ways. The mean quantal content (m) of end‐plate potentials (e.p.p.s) evoked by stimulation of the hypoglossal nerve in c.p. was lower than that of e.p.p.s evoked by stimulation of the regenerated original nerve. The mean latency between stimulation of the implanted nerve and the onset of e.p.p.s was longer than that for stimulation of the original nerve. Stimulation of the foreign nerve often evoked multiphasic e.p.p.s whereas these were only seen on original nerve stimulation during the first 3 months after regeneration. These abnormalities of the foreign innervation persisted for at least 6 months after crushing the original nerve.4. The geniohyoid muscle (which is normally innervated by the hypoglossal nerve) and c.p. appear to contain similar types of muscle fibre. Furthermore, when the geniohyoid muscle became reinnervated by the hypoglossal nerve after it had been crushed, the synapses formed were more effective than those formed by the hypoglossal nerve in c.p.5. Even if reinnervation of c.p. by its nerve was delayed by cutting the brachial nerve at its exit from the vertebral column, the synapses formed by the hypoglossal nerve in c.p. remained abnormal, suggesting that an incompatability exists between the c.p. muscle and the hypoglossal nerve.6. In spite of the differences found between the synapses formed by the hypoglossal nerve and the original nerve in c.p., there was no evidence of regression of the hypoglossal innervation during the period of observation.