bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of duodenal cannulation on abomasal emptying and secretion in the preruminant calf.
Authors: Sissons J W , Smith R H
Published: December 2014

1. The effect of re‐entrant cannulation of the duodenum on digesta flow from, and secretion into, the abomasum of the preruminant calf was studied. 2. Calves fitted with abomasal cannulas and, at the same time or later, with re‐entrant duodenal cannulas were given, by abomasal infusion, test feeds containing glucose and minerals. Net volumes of secretory fluids entering the abomasum and amounts of digesta flowing to the duodenum were estimated from changes in concentrations of water soluble markers (phenol red and polyethylene glycol) in digesta samples collected from an abomasal cannula. 3. Amounts of abomasal contents, net volumes of secretory fluids and digesta flow to the duodenum for calves fitted with only an abomasal cannula did not differ significantly from those obtained for animals with abomasal and re‐entrant duodenal cannulas. 4. Collecting digesta from a re‐entrant cannula and returning it promptly to the animal did not affect net volumes of secretory fluids. Under these conditions with cannulas open to the atmosphere, rather than being connected together, the amounts of digesta entering the duodenum increased slightly but differences were not significant. 5. Weight gains of calves fitted with abomasal and duodenal cannulas were similar to those of intact animals. 6. It is concluded that in calves receiving liquid feeds duodenal re‐entrant cannulation is a suitable preparation for investigating digestive processes of the abomasum.
Effects of stimulation of the chorda tympani in bursts on submaxillary responses in the cat
Authors: Andersson P-O. , Bloom S. R. , Edwards A. V. , Jarhult J.
Published: December 2014

1. The effects of continuous preganglionic stimulation of the chorda tympani at 2 Hz for 10 min were compared with those of stimulation at 20 Hz in 1 sec bursts at 10 sec intervals for the same period in cats treated with atropine (0·5 mg/kg). Both the fall in mean submaxillary vascular resistance (s.v.r.) and the rise in mean vasoactive intestinal peptide (VIP) output from the gland were increased significantly (P < 0·01; P < 0·02) when the same total number of impulses were delivered in the form of bursts at the higher frequency.

2. Both responses were also consistently increased by stimulating the post‐ganglionic innervation in bursts in atropinized cats, or by stimulating the preganglionic innervation in bursts in the absence of atropine.

3. The effects of stimulation of the chorda tympani in 1 sec bursts at 10 sec intervals for 2‐3 min were investigated over the frequency range 2‐160 Hz. The change in mean s.v.r. under these conditions was significantly reduced by administration of atropine at frequencies between 2 and 20 Hz, but not at higher frequencies. In atropinized cats, the fall in mean s.v.r. was linearly related to stimulus frequency (r = 0·993) over the range 2‐60 Hz and a maximal response was obtained during stimulation at 80 Hz. In the same experiments the fall in mean s.v.r. was linearly related to log mean VIP output over the frequency range 20‐160 Hz (r = 0·998).

4. Closely similar changes in mean s.v.r occurred in response to both pre‐ and post‐ganglionic stimulation at all frequencies tested between 2 and 160 Hz in atropinized cats when the stimuli were delivered in bursts. The changes in mean s.v.r. were not significantly affected by varying the duration of individual stimuli over the range 0·1‐25·0 msec.

5. The flow of submaxillary saliva was also linearly related to stimulus frequency over the range 2‐40 Hz (r = 0·997) when the stimuli were delivered in bursts in the absence of atropine and secretion of saliva was maximal at 60 Hz.

6. It is concluded that release of VIP from the submaxillary gland of the cat is optimal in response to stimulation of the chorda tympani at relatively high frequencies, when the impulses are delivered in bursts. Flow of saliva which is mediated by acetyl choline, may also be potentiated under the same conditions.
Cutaneous mechanoreceptors in macaque monkey: temporal discharge patterns evoked by vibration, and a receptor model
Authors: Freeman Alan W. , Johnson Kenneth O.
Published: December 2014

1. Vibratory stimuli applied to the hand of a monkey evoke phase locked impulse trains in the three classes of low threshold mechanoreceptive afferents which innervate the area. The responses of each class of afferent (slowly adapting (SA), rapidly adapting (RA), and Pacinian (PC) vary in a systematic but complex way across the range of frequencies and intensities to which they are sensitive. The receptors are not accessible for electrophysiological recording. The aim in this study was to infer the mechanisms underlying their responses from detailed examination of the statistical properties of the impulse trains.

2. A very simple receptor model with four degrees of freedom was chosen as a starting point. The independent variables consisted of the resting membrane time constant, τ, a variable membrane conductance, Gr, the fraction of each sinusoidal stimulus cycle producing depolarization, pr, and the noise level, σ, which was assigned to the impulse threshold. The aim was to use the deviations between observed data and predictions from the basic model to construct a more effective model. In fact, the deviations were minor and were mostly explained by periods of increased excitability in the wake of each action potential. Almost all of the differences between the responses of the three mechanoreceptive classes examined in this paper were accounted for by differences in time constants.

3. The temporal structure of the responses from each mechanoreceptive class was examined at two levels of resolution, a coarse level where the resolution unit was a full cycle, and a fine level where the unit was 0·1 ms.

4. The coarse structure of each response was represented by the presence or absence of an impulse on each stimulus cycle. In each mechanoreceptive class, the impulse sequences were random at low stimulus frequencies and regular at high frequencies. The transition frequencies were roughly 5 Hz for the slowly adapting afferents, 7 Hz for the rapidly adapting afferents, and 110 Hz for the Pacinian afferents. The model matched these data closely when the time constants were set at 80, 60 and 3·4 ms for SAs, RAs and PCs, respectively.

5. The fine structure of the responses of each mechanoreceptive class exhibited impulse phase locking, phase advance with increasing intensity, and bimodal phase distributions at higher frequencies. Impulses contributing to the first mode of bimodal distributions always occurred in cycles following cycles in which no impulse occurred. Impulses contributing to the retarded mode always occurred in cycles following filled cycles. The mean phase differences between the two modes was called phase retardation. Phase retardation grew with stimulus frequency for both the receptors and the model; the time constants required to match the model against neural phase retardation curves were 123, 64 and 4·8 ms for SAs, RAs and PCs, respectively.
Neurotensin stimulates exocytotic histamine secretion from rat mast cells and elevates plasma histamine levels.
Authors: Carraway R , Cochrane D E , Lansman J B , Leeman S E , Paterson B M , Welch H J
Published: December 2014

1. Neurotensin stimulated histamine release and granule extrusion when applied to isolated rat peritoneal mast cells. 2. This secretory response was prevented by the removal of calcium or energy and was not accompanied by the release of lactic dehydrogenase. 3. The secretory response produced by neurotensin was prevented by prior treatment of mast cells with cromoglycate. 4. The intravenous injection of neurotensin into anaesthetized rats produced a rapid and significant increase in the level of blood histamine that was dependent upon the dose of neurotensin. 5. Treatment of rats with compound 48/80, 24 hr before neurotensin, abolished the elevation in blood histamine caused by neurotensin. The intravenous injection of cromoglycate 1‐2 min before neurotensin greatly reduced the response to neurotensin. 6. The intradermal injection of neurotensin (0.03‐30 p‐mole) increased capillary permeability in rats pre‐treated intravenously with Evans Blue. This response was abolished by the antihistamine, diphenhydramine. Increasing the dose of neurotensin to 300 p‐mole partially overcame this inhibition by diphenhydramine. 7. Our results demonstrate that neurotensin can elicit an exocytotic secretory response from isolated rat peritoneal mast cells and elevate histamine levels in blood. It is suggested that some of neurotensin's physiological effects may be due to stimulation of mast cell secretion.
Branching of muscle spindle afferents of jaw closing muscles in the cat.
Authors: Kato T , Kawamura Y , Morimoto T
Published: December 2014

1. Functionally isolated single fibres were prepared from the cut central ends of the masseter nerve in cats. Of those firing in response to muscle stretch, most were alpha motor units but some had the properties of afferent fibres innervating muscle receptors. 2. These afferent units were remarkably sensitive to muscle stretch even under anaesthesia deep enough to eliminate all stretch evoked e.m.g. activity in masseter. Moreover, these units responded to gentle pressing of the surface of either the masseter, temporalis or pterygoid muscles. 3. On the basis of their responses to ramp stretch, to high‐frequency vibration, to suxamethonium, and to gentle pressing of the muscle surface, the majority were considered to arise from primary or secondary endings of muscle spindles. 4. In reflexly induced jaw movements, the highest discharge frequency of these spindles was observed during the jaw opening phase. However, they were also activated during the jaw closing phase, indicating that the fusimotor innervation to the source spindle was still preserved. 5. From these results, it is concluded that branching of the spindle afferent outside the capsule occurs in the muscle nerve innervating cat's jaw closing muscles.
Correlation between the preferred orientation and spatial frequency of neurones in visual areas 17 and 18 of the cat.
Authors: Berardi N , Bisti S , Cattaneo A , Fiorentini A , Maffei L
Published: December 2014

1. In seventy‐six penetrations through areas 17 and 18 of the cat, neurones were regularly sampled at intervals of 100 micrometers and preferred orientation, optimal spatial frequency and resolving power were determined for each neurone in response to drifting sinusoidal gratings. 2. As already shown for area 17, in tangential penetrations through area 18, whenever the preferred orientation rotates progressively from cell to cell, the optimal spatial frequency tends to remain constant. 3. A statistical analysis on 1574 cells in areas 17 and 18 showed that for pairs of cells separated 200‐300 micrometers along a track the difference in preferred orientation delta alpha and the difference in optimal spatial frequency delta f are not randomly distributed: cell pairs with small delta alpha are most likely to have large delta f and vice versa. 4. These findings indicate that in areas 17 and 18 neurones with the same optimal frequency are aligned along a direction orthogonal to the orientation columns. 5. The optimal spatial frequency, resolving power and the velocity cut‐off were averaged for cells from different penetrations located in the same cortical layer or sublayer of area 18: mean optimal spatial frequency and acuity are highest in layer IV and lowest in layers II and V, while the velocity cut‐off is highest in layers II and V and lowest in layer IV. 6. Our data suggest that the layering of cells according to optimal spatial frequency is a more subtle subdivision than the six histological layers.
The effects of stimulation rate on calcium‐dependent action potentials recorded from chick embryo heart cell aggregates.
Authors: Mackenzie E , Standen N B
Published: December 2014

1. Action potentials were recorded from aggregates of heart cells prepared from 3‐ to 7‐day chick embryos. At 3 days the maximum rate of rise (+ Vmax) was insensitive to TTX; at 7 days it was considerably reduced by TTX. 2. In the presence of TTX the action potential overshoot was dependent on [Ca]0; the results may be fitted using constant field theory and assuming that the membrane is over a hundred times more permeable to Ca than to Na or K. 3. An increase in stimulation rate in the range 0.2‐2 Hz led to an increase in both overshoot and + Vmax. This effect was not seen after addition of 20 mM‐tetraethylammonium ions, nor when Sr was substituted for Ca in the external medium. We suggest that these rate‐dependent changes may result from partial inactivation of an outward K current.
The effect of pseudopregnancy on glomerular filtration rate and salt and water reabsorption in the rat.
Authors: Atherton J C , Bu'lock D , Pirie S C
Published: December 2014

1. Glomerular filtration rate (G.F.R.) and salt and water reabsorption were measured in age‐matched virgin rats and rats at different stages of pseudopregnancy and post‐pseudopregnancy. 2. Tubular reabsorption and G.F.R. were significantly higher in later pseudopregnancy. Values at mid‐pseudopregnancy were intermediate between virgin controls and late‐pseudopregnancy. In post‐pseudopregnancy G.F.R. and reabsorption had returned to values not different from the virgins. 3. Expansion of extracellular fluid volume (e.c.f.v.) and elongation of proximal tubules were observed during pseudopregnancy. In post‐pseudopregnancy increased tubular length was still apparent but e.c.f.v. was not. 4. The remarkable similarity in the changes in e.c.f.v. and renal functions and structure during pseudopregnancy to those in early pregnancy suggests that the feto‐placental unit is not necessary for the pregnancy changes. 5. The differences between the time course of change in plasma progesterone and the time courses of changes in e.c.f.v., renal functions and tubular morphology in late pseudopregnancy suggest that progesterone is not directly involved.
Plasma secretion and pancreatic secretion in response to liver extract meal with varied pH and exogenous secretin in the dog.
Authors: Chey W Y , Konturek S J
Published: December 2014

1. In dogs with chronic gastric and pancreatic fistulas, a liver extract meal adjusted to various pH levels ranging from 7.0 to 2.0, was introduced into the stomach and the increments in plasma secretin levels were correlated with the pH of the liver extract meal and pancreatic bicarbonate outputs. 2. The pH threshold for both bicarbonate secretion and secretin release was found to be about 4.5. With a stepwise decrease in the pH of the meal below pH 4.5, there were stepwise increments in the plasma secretin concentrations and pancreatic bicarbonate outputs. 3. Exogenous secretin, given in graded doses ranging from 0.03 to 2.0 clinical unit/kg per hr, increased the plasma secretin concentrations and bicarbonate secretion in a dose‐dependent fashion. 4. These results indicate that the pH threshold for release of endogenous secretin is 4.5 and suggests that, at pH levels below 4.5, pancreatic bicarbonate secretion depends upon the duodenal acid load and is linearly correlated to an increment in plasma secretin concentrations. 5. It is concluded that endogenous secretin is a major determinant of pancreatic bicarbonate secretion after a meal. 6. Pancreatic protein secretion by intragastric liver extract meal was greatly increased both in experiments with liver extract meal, pH 4.0 or below, and I.V. infusion of secretin at a dose of 0.12 u./kg per hr. It is questioned, however, whether this effect of secretin is physiological.
Effects of picrotoxin and strychnine on non‐linear responses of Y‐type cat retinal ganglion cells.
Authors: Frishman L J , Linsenmeier R A
Published: December 2014

1. The effects of neurotransmitter antagonists on spatially linear and non‐linear responses of Y cat retinal ganglion cells were studied. 2. The contrast sensitivity of the spatially linear receptive field centre and surround at mesopic and photopic levels of illumination was affected very little by picrotoxin, but the sensitivity of the non‐linear subunits was reduced. 3. Picrotoxin also reduced two other non‐linear effects: ‘shift responses’ and the suppression of the response to a centred test flash caused by movement of a peripheral pattern. 4. In contrast to picrotoxin, strychnine decreased the contrast sensitivity of the receptive field centre, and increased the sensitivity of the subunits. 5. The results support the idea that the non‐linear responses may all be generated by similar pathways, which are distinct from those which generate linear responses. Because both picrotoxin and strychnine affect subunit responses, cells using gamma‐aminobutyric acid (GABA) and glycine as transmitters are probably involved in subunit pathways.
The effect of transient stimulation of lung irritant receptors on the pattern of breathing in rabbits.
Authors: Davies A , Roumy M
Published: December 2014

1. 100 ms pulses of inflation and deflation were applied to the lungs of anaesthetized rabbits before and during inactivation of pulmonary stretch receptors. 2. Pulses of either sign given in inspiration often produced augmented breaths, whether or not stretch receptors were inactivated. Inflation pulses were more effective than deflation pulses. 3. After an augmented breath it was impossible to produce another for at least 1 min (refractoriness). 4. Pulses of deflation always shortened expiration. Pulses of inflation early in expiration shortened expiration. Later in expiration they lengthened expiration when stretch receptors were active and shortened expiration when stretch receptors were blocked. No refractoriness was observed for the effects on expiratory time. 5. Pulses in paralysed animals caused a burst of phrenic activity of fixed duration, usually with brief latency. There was no refractoriness. 6. We suggest that the duration of inspiration is governed by the activity of pulmonary stretch receptors, except during an augmented breath, and that the duration of expiration is governed by a balance of stretch and irritant receptor activity.
A micro‐electrode study of oligopeptide absorption by the small intestinal epithelium of Necturus maculosus.
Authors: Boyd C A , Ward M R
Published: December 2014

1. The effects of some amino acids and oligopeptides on the electrical properties of the brush‐border membrane of the small intestine of the mudpuppy, Necturus maculosus were studied in vitro using micro‐electrodes. 2. A number of amino acids (glycine, L‐proline and L‐leucine) and small peptides (carnosine, glycyl‐L‐proline, L‐leucyl‐L‐leucine, glycylglycine and glycylglycylglycine) depolarized the brush‐border membrane. This was associated with a reduction of input resistance. Tetraglycine did not appreciably reduce the membrane potential. 3. Evidence is presented that the electrical effects caused by application of the peptides are not solely due to the effects of the products of peptide hydrolysis. Furthermore there appears to be more than a single system available to the peptides. 4. Stereospecificity is found for both amino acids and peptides but appears to be more marked for the peptides. 5. Peptide‐induced depolarizations are less markedly reduced in the absence of external Na+ than are the depolarizations caused by the amino acids. 6. These results are discussed with respect to the mechanism and significance of amino acid and peptide transport in the intestinal tract.
The formation of appropriate central and peripheral connexions by foreign sensory neurones of the bullfrog
Authors: Frank Eric , Westerfield Monte
Published: December 2014

1. The ability of foreign sensory neurones to form novel reflex pathways was studied in bullfrogs by removing, during early larval stages of development, the dorsal root ganglion (d.r.g. 2) that normally provides the entire sensory innervation of the front limb.

2. After the operation these tadpoles metamorphosed into frogs that responded to sensory stimuli and had nearly normal use of the limb. Sensation in the limb was mediated by sensory neurones located in an adjacent ganglion (d.r.g. 3); these neurones normally never grow into the arm.

3. These neurones were shown, by labelling with horseradish peroxidase, to project into the arm and into the region of the brachial spinal cord occupied by motoneurones innervating muscles in the arm. These projections do not occur at any time during normal development.

4. Intracellular recordings from identified motoneurones demonstrated that when the operations were done before developmental stage 9 appropriate monosynaptic sensory‐motor pathways were established. The relative strengths of synergistic and antagonistic sensory projections onto motoneurones were normal, although the latencies of the synaptic potentials were somewhat longer.

5. When the operation was performed after stage 9 but before metamorphosis, d.r.g. 3 sensory afferents grew into the arm and into the brachial spinal cord but did not make monosynaptic connexions onto motoneurones.

6. Removal of d.r.g. 2 from adult bullfrogs failed to produce either central or peripheral changes in the projections of d.r.g. 3 sensory neurones.

7. Many d.r.g. 3 neurones still innervated their normal sensory targets in the thorax. These neurones never formed monosynaptic connexions onto brachial motoneurones in either normal or experimental animals. In experimental animals, the polysynaptic projections of these third nerve sensory neurones to brachial motoneurones were stronger than in normal animals independent of when d.r.g. 2 was removed during development.

8. Thus foreign sensory cells can form specific, functionally appropriate connexions between peripheral targets and motoneurones if the sensory cells that normally mediate this reflex pathway are removed sufficiently early during development.
Ion flux changes induced by voltage clamping or by amphotericin B in the isolated urinary bladder of the trout.
Authors: Fossat B , Lahlou B
Published: December 2014

1. When bathed with Ringer solutions on both sides in Ussing chambers, isolated urinary bladders of trout carry out an electrically silent transport of Na+ and Cl‐ ions from mucosa to serosa. In the present experiments, an electrical gradient was set up across the epithelium mounted under these conditions either by using a voltage‐clamp technique or by submitting the mucosal side to the polyene antibiotic Amphotericin B. 2. With stable potential differences between ‐40 and +40 mV applied to the tissue, both unidirectional fluxes (Jms and Jsm) for Na+ and for Cl‐ varied as a function of the electrical gradient. This indicates that a sizeable fraction of these ionic exchanges is due to passive diffusion across a low‐resistance pathway. 3. Amphotericin B (40 micrograms/ml.) applied to the mucosal side induced an immediate and large (up to 50 mV, serosa positive) potential difference and a sustained diminution in tissue resistance. These effects were strictly Na+‐dependent and were reduced in the presence of ouabain. Therefore they are due to increased passive entry of Na+ along its electrochemical gradient across the cellular apical membrane. 4. The effect of Amphotericin B was enhanced when Cl‐ was replaced by an impermeant anion such as gluconate. Therefore the shunting effect of Cl‐ on the induced potential observed in the control conditions appears to be due to an increase in Cl‐ permeability across an anion pathway. Flux data indicate that this pathway is transcellular.
Temperature dependence of tetrodotoxin effect in squid giant axons.
Authors: Sevcik C
Published: December 2014

1. The effects of temperature changes from 30 to 5 degrees C on some properties of giant axons of the squid Doryteuthis plei were studied under voltage‐clamp conditions. 2. The maximum inward sodium current of giant axons held at their normal resting potential decreases from 8 to 2 mA/cm2 when the temperature is lowered from 21 to 5 degrees C. 3. The effect of tetrodotoxin on those axons and its steady‐state kinetics are markedly temperature dependent. It appears that there are two types of receptors in squid axon membranes, which differ in their temperature dependence. 4. One group of receptors (type 1) increases its affinity for the toxin when the temperature is increased (maximum affinity at 30 degrees C, K1 = 0.03 +/‐ 0.01 nM). The other group of receptors (type 2) shows an increase in its affinity when the temperature is lowered (maximum affinity at 5 degrees C, K2 = 0.07 +/‐ 0.02 nM). At 10 degrees C the two populations have the same affinity (K1 = K2 = 0.67 +/‐ 0.06 nM).
The relation between tonicity and impulse‐evoked transmitter release in the frog
Authors: Kita Hiroshi , Narita Kazuhiko , van der Kloot William
Published: December 2014

1. The increase in miniature end‐plate potential (m.e.p.p.) frequency in response to tetanic stimulation of the motor nerve at frog neuromuscular junctions in Ca2+‐free, Mg2+ EGTA‐containing (0 Ca2+—Mg2+ EGTA) solutions of varying tonicity has been studied. The response to stimulation is markedly increased in hypertonic solutions and is decreased in hypotonic solutions. Under these conditions changes in tonicity have comparable effects on stimulated and spontaneous quantal release.

2. The tonicity was raised by adding sucrose, NaCl or glycine to the extracellular solution. The effects of the addition depended primarily on the increase in osmolarity of the solution, not on the chemical species producing it.

3. The tonicity was decreased by lowering [NaCl]o. The hypotonic solution decreased the response to tetanic stimulation. When the tonicity of the solution with the low [NaCl]o was restored to normal by adding sucrose, the response was restored to its usual level. These results suggest that in 0 Ca2+—Mg2+ EGTA solutions stimulation does not enhance the probability of quantal release by raising [Na+]i.

4. Repeated bouts of tetanic stimulation produced almost identical responses. In some instances the frequency continued to rise after the end of the tetanic stimulation, as reported by Erulkar & Rahamimoff (1978). This suggests that the stimulation of the nerve leads to the elevation within the terminal of a substance that in turn liberates an activator for quantal release.

5. The Q10 for the increase in probability of quantal release is as high as 7. High Q10 values have also been reported for spontaneous m.e.p.p. frequencies. Tonicity and temperature appear to affect spontaneous and stimulated quantal release similarly.
Acetylcholine measured at short time intervals during transmission of nerve impulses in the electric organ of Torpedo
Authors: Dunant Y. , Jones G. J. , Loctin Françoise
Published: December 2014

1. The amounts of total acetylcholine (ACh) and ATP, and of vesicle‐bound ACh were measured at short time intervals in the electrogenic tissue of Torpedo marmorata. The aim of this study is to approach with biochemical analysis the speed of electrophysiological phenomena.

2. A stimulator coupled to a rapid freezer device was used to quench a number of tissue samples simultaneously, at different time intervals during transmission of a brief train of impulses at 100 Hz.

3. The level of total ACh decreased significantly with the first ten impulses. Then a rapid but transient increase in total ACh occurred, reaching a maximum value by the fifteenth to sixteenth impulse.

4. Vesicle‐bound ACh did not exhibit any changes parallel to those of total ACh, and did not decrease beyond the control level during transmission of twenty impulses at 100 Hz.

5. The amount of ATP in the tissue varied in close relation to that of total ACh. No significant phase shift was observed between the transmitter and the nucleotide and the ACh/ATP molar ratio was not significantly different from 1.

6. The shortest time interval investigated in this work was 10 ms. The rate at which the pieces of tissue are quenched for biochemical measurements when plunged into a liquid at low temperature has been estimated. It has also been evaluated to what extent the freezing rate may distort measurements of the biochemical changes occurring in the tissue.

7. It is concluded that fast freezing appears to be a valuable approach for investigating the rapid biochemical changes underlying cholinergic transmission; a better time resolution might be reached at the price, however, of greatly reducing the size of the samples. The second conclusion is that transmission of a brief train of impulses is accompanied by significant changes in the amount of extravesicular ACh.
Lateral hypothalamic neurones: osmosensitivity and the influence of activating magnocellular neurosecretory neurones
Authors: Leng G.
Published: December 2014

1. The activity of single cells in the supraoptic nucleus and the lateral hypothalamus of urethane‐anaesthetized rats was studied during electrical stimulation of the neural stalk.

2. Neurones activated antidromically from the neural stalk were either unaffected or, rarely, slightly affected by single shocks or by brief trains of shocks presented at an intensity just below that necessary for antidromic invasion. Thus there does not appear to be a strong synaptic coupling between rat supraoptic neurones.

3. In contrast, many lateral hypothalamic neurones, and particularly those in the perinuclear zone, were strongly affected by neural stalk stimulation, being either orthodromically excited or inhibited. Thus, rat magnocellular neurosecretory neurones appear to project, directly or indirectly, to the lateral hypothalamus.

4. Thirty‐one lateral hypothalamic neurones were studied following an I.P. injection of 1 ml. 1·5 M‐NaCl. Eighteen neurones responded to this osmotic stimulus with a change of at least 1 spike/sec in mean firing rate.

5. Fifteen of the thirty‐one neurones were strongly affected by neural stalk stimulation (eight inhibited, seven excited). Ten of these fifteen neurones were affected in the same way by osmotic stimulation. The remaining sixteen out of thirty‐one neurones were unresponsive to neural stalk stimulation, and of these, ten were also unresponsive to osmotic stimulation. Thus most lateral hypothalamic neurones responded in a similar way to neural stalk stimulation and to systemic osmotic stimulation.

6. Thus the osmosensitivity of some neurones in the lateral hypothalamus may be mediated by synaptic input arising from the magnocellular neurosecretory neurones. However, the osmosensitivity of some lateral hypothalamic neurones cannot be explained in this way, and probably derives from osmoreceptors other than the magnocellular neurones.
Expanded receptive fields of cutaneous mechanoreceptor cells after single neurone deletion in leech central nervous system.
Authors: Blackshaw S E , Nicholls J G , Parnas I
Published: December 2014

1. Individual sensory neurones responding to touch (T) and to noxious (N) stimuli applied to the skin of the leech were killed by injecting pronase into their cell bodies, situated within the C.N.S. This procedure destroys one neurone in its entirety without damaging the cells. 2. When three out of four N cells within a ganglion have been killed, the receptive field of the remaining N sensory cell expands to cover the denervated area of skin. Similarly the field of the touch cell that innervates dorsal skin spreads across the mid line to innervate contralateral skin after the three touch cells on that side have been deleted. 3. The spread is graded and develops with time. The earliest effects appear within 4 weeks and the full spread develops by 3 months. 4. No detectable spread of receptive fields occurs if only two N cells, one on each side, are killed. 5. Following deletion of N cells, the receptive fields of T and pressure sensory cells are unaffected. Similarly, if T cells have been killed, the fields of N cells or pressure cells do not become enlarged. 6. These results represent a modality‐specific mechanism by which one sensory cell can be influenced to extend the territory it supplies in the periphery in response to a minimal lesion without its own terminals having been damaged.
Reduction of the bradykinin‐induced activation of feline group III and IV muscle receptors by acetylsalicylic acid.
Authors: Mense S
Published: December 2014

1. In chloralose‐anaesthetized cats, the influence of systemically or locally applied acetylsalicylic acid (ASA) on the responses of thin‐fibre muscle receptors to close‐arterial injections of bradykinin was studied. 2. Many of the slowly conducting (group III and IV) muscle afferents had a background activity of low frequency. This discharge was either unaffected or slightly increased by the ASA doses used. In two units which had a very high discharge rate ASA led to a marked decrease in background activity. 3. On local (I.A. or I.M.) injection of ASA, doses below 1 mg were sufficient for reducing the bradykinin‐induced activations of group III and IV muscle receptors. The reduction lasted for about 15‐30 min. 4. On systemic (I.V.) administration of ASA (50 mg/kg body weight) the reduction in response magnitude to bradykinin became significant 8 min after injection of the analgesic. The effect was maximal about 10 min later and lasted for more than 60 min. 5. Five receptors were found which gave a repeated response to 5‐hydroxytryptamine (5‐HT) injected at 10 min intervals. The 5‐HT‐induced activations could not be reduced by ASA (50 mg/kg I.V.). 6. Most of the receptors responding to bradykinin had a high threshold on mechanical stimulation and thus were probably nociceptors. It is concluded that the reduction of their bradykinin‐induced activations reflects the suppression of nociceptive information by an analgesic. Since the recordings were obtained from primary afferent units the data constitute direct evidence for a peripheral action of ASA.
An analysis of a thermal afferent pathway in the rat
Authors: Hellon R. F. , Taylor David C. M.
Published: December 2014

1. Single unit activity has been recorded in the thalamic, hypothalamic and raphe magnus nuclei of rats anaesthetized with Urethane.

2. Neurones were sought which responded to changes in scrotal skin temperature applied with a water‐perfused brass thermode. All sixty‐nine neurones in the thalamus and hypothalamus responded with abrupt changes in activity as the scrotum was warmed (‘switching response’). The majority responded with an increase in activity from minimal to maximal firing rate as the scrotum was warmed over a range of less than 0·5 °C; in about 20% of the neurones the converse was observed.

3. To determine whether the switching response of the thalamic and hypothalamic neurones depended upon a cortico‐thalamic feed‐back loop, the cortical surface was cooled to 18‐20 °C to reversibly abolish cortical post‐synaptic activity.

4. Cortical cooling abolished the positive switching response of nearly all (15/19) ventrobasal thalamic neurones to scrotal warming. All eight ventrobasal thalamic neurones with negative switching responses, and all twenty‐two scrotal temperature‐responsive neurones in other thalamic and hypothalamic nuclei were unaffected.

5. Twenty recordings were also made from scrotal temperature‐responsive neurones in the nucleus raphe magnus. All possessed switching responses similar to those observed in the thalamus and hypothalamus.

6. None of the scrotal temperature‐responsive neurones in the nucleus raphe magnus was affected by cortical cooling. Six neurones were observed in decerebrate rats with properties apparently identical to those in intact rats.

7. We conclude that the switching response of thalamic and hypothalamic scrotal temperature‐responsive neurones is probably generated in the nucleus raphe magnus and passed in parallel to the thalamus and hypothalamus. In addition, thalamic neurones depend on an intact link with the cerebral cortex for the generation of their switching responses.
Depolarization produced by sodium removal in the circular muscle of the guinea‐pig stomach.
Authors: Sakamoto Y , Tomita T
Published: December 2014

1. Reducing the Na concentration to less than 20 mM depolarized the circular muscle of the guinea‐pig stomach and contracture developed. The rate of depolarization varied between preparations. In some, all electrical activity disappeared within 2‐3 min in Na‐free solution, accompanied by depolarization, but in other preparations a sinusoidal rhythmic activity remained for various lengths of time up to 10 min. 2. When Ca was removed after the depolarization in Na‐free solution was fully developed, the membrane partly repolarized and the contracture was abolished. Addition of 2 mM‐Mn in the presence of Ca had the same effect. 3. After complete block of electrical activity in Ca‐free and Na‐free solution, readmission of only Ca (2.5‐50 mM) produced sinusoidal rhythmic activity. This activity, observed in the absence of Na, was abolished when the membrane was hyperpolarized by applying inward current. 4. The membrane depolarized in Na‐free solution was repolarized by readmission of only 5 mM‐Na. This repolarization was greater and faster when the exposure to Na‐free solution was prolonged. 5. The possibility was considered that an electrogenic Na‐Ca exchange may be involved in the generation of the first component of the slow wave, and that removal of Na blocked the repolarizing phase of this component. In the absence of Na, Ca can evoke rhythmic activity and the underlying mechanism may be the same as that of the second component of slow wave, i.e. an increase in Ca conductance.
Response properties of rat olfactory bulb neurones
Authors: Mair R. G.
Published: December 2014

1. Response properties of rat olfactory bulb neurones were studied by recording single‐unit activity evoked by stimuli delivered by an air‐dilution olfactometer. Neural responses were quantified as peristimulus time histograms by averaging the responses evoked by eight presentations of the same stimulus. Animals were stimulated by means of controlled artificial sniffs produced by a vacuum source connected to the choana.

2. Evoked activity was divided into on‐ and after‐responses. Three types of on‐responses were distinguished on the basis of temporal patterns of activity evoked by odorous stimuli. Neurones exhibited the same type of response when driven by different odorants. For a given neurone, the size of an evoked response depended on the odorant used as a stimulus substance. The stimulating effectiveness of particular odorants varied between different neurones.

3. After‐responses were divided into two classes: phasic (0·5‐3 sec after stimulus offset) and tonic (3 sec—2 min after stimulus offset). After‐responses were associated with a subset of neurones making each type of on‐response and with units producing no clear on‐response. It is suggested that the occurrence of an after‐response in a given neurone is not dependent on the nature of the evoked on‐response.

4. Intensity‐related changes of on‐responses were characterized by three measures: number of action potentials evoked during the stimulus event, latency of action‐potential bursts, and rate of activity during the action‐potential bursts. The number of evoked action potentials was not monotonically related to stimulus concentration. In contrast, there was a clear relationship between the pattern of evoked activity and stimulus concentration.

5. It is proposed that the timing of excitation and inhibition is dependent on the concentration of the stimulus and that the number of evoked action potentials depends on the odorant used as a stimulus substance and the concentration at which it is delivered.
Adaptation of rat olfactory bulb neurones.
Authors: Mair R G
Published: December 2014

1. Single‐unit activity was recorded from olfactory bulb neurones driven by odorous stimuli. Neural responses were quantified as averaged peristimulus time histograms. 2. Successive presentations of the same stimulus evoked similar patterns of activity during each presentation. Some neurones exhibited increased and others decreased excitability in the adapted state. The occurrence of such facilitative or suppressive self‐adaptation was not determined by odorant concentration or by the number of action potentials evoked by a given stimulus. Neurones driven by more than one odorant exhibited the same type of adaptation (facilitative or suppressive) for all effective stimuli. 3. When the first odorant differed from the second, the number but not the pattern of action potentials evoked by the second odorant differed from the non‐adapted state. Some neurones exhibited increased and others decreased excitability in the cross‐adaptation state. Neurones exhibiting suppressive self‐adaptation did not exhibit facilitative cross‐adaptation and those exhibiting facilitative self‐adaptation did not exhibit suppressive cross‐adaptation. Instances of asymmetrical cross‐adaptation were noted in which two odorants differed in the extent to which they affected subsequent sensitivity to each other. The degree of symmetry for a given pair of odorants differed for different neurones. It is concluded that neurones in the olfactory bulb differ in both the type (suppressive or facilitative) and extent of adaptation evoked by a given odorant.
The post‐natal development of cholecystokinin‐like activity in the brain and small intestine of the rat.
Authors: Brand S J
Published: December 2014

1. The post‐natal development of cholecystokinin (CCK)‐like activity was studied in the brain and small intestine of the rat. CCK‐like biological activity was measured in extracts of these tissues by an in vitro rabbit gall‐bladder bioassay. 2. Immediately after birth, the brain contained very little CCK‐like activity whereas the proximal small intestine contained significant concentrations of CCK‐like activity. The concentration of CCK‐like activity in the brain increased rapidly during the third post‐natal week and reached adult values by the end of the fourth week. The development of CCK‐like activity in the proximal small intestine differed from that seen in the brain. The concentration of CCK‐like activity increased during the first post‐natal week. After this time, however, the concentration decreased and the adult values, therefore, were lower than those found immediately after birth. This decrease in concentration resulted from failure of the total content of CCK‐like activity to increase despite rapid growth of the intestine. 3. The composition of CCK‐like activity in neonatal extracts was determined by gel filtration chromatography with Sephadex G50. Extracts of neonatal brain and intestine contained more than one molecular form of CCK‐like activity in contrast to the single peak of activity found in adult extracts. In the developing intestine smaller molecular forms were found in addition to the single larger form found in the adult and in the neonatal brain larger molecular forms were found in addition to the CCK octapeptide found in the adult.
The pattern of cardiovascular response to carotid chemoreceptor stimulation in the cat.
Authors: Hilton S M , Marshall J M
Published: December 2014

1. The pattern of cardiovascular response evoked by carotid chemoreceptor stimulation has been investigated in cats anesthetized by continuous infusion of Althesin (Glaxo). 2. A variety of chemoreceptor stimulants, injected retrogradely into the lingual artery with the external carotid artery ligated, evoked hyperventilation with variable changes in arterial pressure and heart‐rate, but a consistent vasodilatation in limb muscles and vasoconstriction in renal, mesenteric and cutaneous vasculature. 3. The muscle vasodilatation was still obtained after vagotomy and when the animal was paralysed and artificially ventilated; thus, it was not secondary to the hyperventilation. 4. In the majority of experiments the muscle vasodilatation was much reduced or abolished by atropine indicating it was mediated by sympathetic cholinergic fibres, which is characteristic of the alerting stage of the defence reaction in the cat. The cardiovascular pattern was accompanied by the other autonomic features of the alerting response, viz. pupillary dilatation, retraction of the nictitating membranes and pilo‐erection. 5. In one and the same animal the pattern of response evoked by carotid chemoreceptor stimulation was the same as that evoked by noxious cutaneous stimulation, and by electrical stimulation in the brain stem defence areas. 6. It is concluded that peripheral chemoreceptor stimulation acts as an excitatory input to the hypothalamic and brain stem defence areas and that it can readily evoke the autonomic components of the alerting stage of the defence reaction. It is suggested that this has been missed in previous studies on anaesthetized animals because of the depressant action of chloralose and barbiturates on transmission in the hypothalamus and mid‐brain.
Effects of goniopora toxin on non‐adrenergic, non‐cholinergic response and purine nucleotide release in guinea‐pig taenia coli
Authors: Fujiwara Motohatsu , Hong Sung‐Cheul , Muramatsu Ikunobu
Published: December 2014

1. Effects of goniopora toxin (GPT) on non‐adrenergic, non‐cholinergic inhibitory responses were examined in isolated guinea‐pig taenia coli and the transmission mechanism was analysed.

2. GPT (20‐50 nM) gradually augmented the relaxation and rebound contraction induced by electrical transmural stimulation in the presence of guanethidine and atropine. These effects were abolished by tetrodotoxin.

3. The resting tension and the response to exogenously applied ATP were little affected by GPT.

4. The action potentials and the electrotonic potentials recorded by a double sucrose‐gap method were little affected by GPT.

5. These results indicate that the augmentation is elicited by a direct action of GPT on the non‐adrenergic, non‐cholinergic neurones, rather than on the smooth muscles per se.

6. GPT augmented the amplitude of the inhibitory junction potential (i.j.p.) recorded in the presence of guanethidine and atropine. GPT also enhanced the 3H efflux in response to electrical transmural stimulation of preparations pre‐loaded with [3H] adenosine. Tetrodotoxin markedly inhibited or abolished the i.j.p. and 3H efflux.

7. These results would suggest that augmentation of the non‐adrenergic, non‐cholinergic responses is due to increased transmitter release from the nerve. Under conditions in which the transmitter release was augmented, the non‐adrenergic, non‐cholinergic response showed an essentially similar pattern to that obtained under normal conditions; therefore the inhibitory response is probably due to a putative transmitter, possibly ATP or a related nucleotide.
Amino acid inhibition and stimulation of 2‐aminoisobutyric acid exit from anuran small intestine
Authors: Boyd C. A. R. , Perring Vivien S.
Published: December 2014

1. Using the vascularly perfused frog small intestine, the exit of the non‐metabolized amino acid 2‐aminoisobutyric acid (AIB) from the pre‐loaded epithelium into the blood has been studied in winter animals.

2. Marked inhibition of the instantaneous rate constant for AIB exit into the vascular bed is observed when L‐leucine, but not D‐leucine, is added either to the intestinal lumen or to the vascular bed. The extent of the inhibition is related to the leucine concentration in an alinear fashion. The concentration of luminal L‐leucine giving half maximal inhibition is 2·5 mM.

3. The instantaneous rate constant for AIB exit is similarly decreased by 10 mM‐L‐tryptophan and by L‐phenylalanine added to the intestinal lumen and to a lesser extent by L‐asparagine, L‐valine, L‐glutamine, L‐isoleucine, and L‐norleucine.

4. 10 mM‐L‐proline added to the lumen stimulates AIB exit from the pre‐loaded epithelium into the blood. This stimulation is due to an increased rate constant for movement of AIB across the basolateral membrane.

5. No inhibition is found when the dipeptide L‐leucyl‐L‐leucine (10 mM) is added to the intestinal lumen in the presence of 10 mM‐L‐leucine. When added to the vascular compartment this dipeptide has no effect upon AIB exit from the epithelium.

6. Possible mechanisms by which amino acids and peptides may influence AIB movement out of the epithelium into the blood are discussed and conclusions are drawn concerning AIB transport across the intestinal basolateral membrane of the intact epithelium.