bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
The effects of vasoactive intestinal peptide on neuromuscular transmission in the frog
Authors: Gold Michael R. 
Published: December 2014

1. The effects of vasoactive intestinal peptide (VIP) on cholinergic transmission were studied at the neuromuscular junction of the frog.2. Bath application of VIP (10−8‐10−7 M) produced a dose‐dependent increase in quantal content of the end‐plate potential (e.p.p.), while having no effect on quantal size or on resting membrane potential of the muscle fibres.3. The increases in e.p.p. amplitude observed at end‐plates blocked with Mg2+ or curare were comparable.4. VIP increased miniature end‐plate potential frequency when the nerve terminal was depolarized with K+. This effect was abolished by removing Ca2+ from the bathing solution.5. Ionophoretic application of VIP to the end‐plate also increased quantal content, while having no effect on quantal size or on the input resistance and resting membrane potential of the fibres.6. Some possible mechanisms for the action of VIP are discussed, and it is proposed that it may act on some step involved in depolarization—secretion coupling.
Asynchronous respiratory activity of the diaphragm during spontaneous breathing in the lamb
Authors: Henderson‐Smart D. J. , Johnson P. , McClelland Mary E. 
Published: December 2014

1. Direct simultaneous recordings from chronically implanted electrodes in different parts of the diaphragm were made in young lambs in which laryngeal adductor (thyroarytenoideus) and intercostal electromyograms, airflow, tracheal pressure and electrocorticogram and electro‐oculograms for behavioural state were also recorded.2. An asynchrony of diaphragmatic contraction occurred which was dependent on sleep state. The vertebral portion showed maximal post‐inspiratory activity while the lateral paratendinous portion usually terminated abruptly with end‐inspiration, reciprocating closely with the onset of expiratory laryngeal adductor activity during quiet sleep. The contraction of the sternal portion was similar to the vertebral portion. In active (rapid eye movement) sleep there was no expiratory laryngeal constriction and post‐inspiratory activity occurred in all portions of the diaphragm. During the characteristic bursts of rapid breathing in active sleep all post‐inspiratory activity disappeared and the diaphragm contracted synchronously.3. General anaesthesia (Halothane/N2O or Nembutal) abolished expiratory laryngeal adductor activity and the discharge pattern became similar in all parts of the diaphragm.4. Intrathoracic vagotomy of Xylocaine blockade below the recurrent laryngeal nerves abolished post‐inspiratory activity in all parts of the diaphragm, in contrast to the effect on expiratory laryngeal adductor activity which increased.5. Sustained ‘tonic’ electromyographic activity was often recorded from the costal and to a lesser extent the paratendinous portion of the diaphragm. This activity related to adjacent intercostal activity:ipsilateral intercostal blockade with local anaesthetic (Xylocaine 1%) abolished both the intercostal and the ‘tonic’ activity of the costal margins of the diaphragm. Conversely ipsilateral phrenic nerve blockade abolished all but the ‘tonic’ activity which related to intercostal activity.6. Interpretation of the respiratory activity of the diaphragm could not be made adequately from conventionally placed electrodes (i.e. costal, sternal slip or surface) during spontaneous breathing in unanaesthetized lambs. Simultaneous recordings showed that while expiratory flow and duration were actively controlled by expiratory laryngeal adductor activity and the diaphragm, the latter performed asynchronously. While both laryngeal and diaphragmatic expiratory functions were substantially under vagal control, the former increased and the latter decreased with reduced vagal input.
Accurate repositioning of the human thumb against unpredictable dynamic loads is dependent upon peripheral feed‐back
Authors: Day B. L. , Marsden C. D. 
Published: December 2014

1. The strategy of accurate movement of the human thumb has been studied in nine subjects. An open‐loop hypothesis, which states that a new final position is defined by re‐setting the agonist/antagonist spring constants, was tested2. Subjects were trained to flex the top joint of the thumb rapidly through 20 deg in about a third of a second from a fixed starting position against a load. Occasionally, and unpredictably, the viscous friction of the load was altered prior to it's being moved. The spring hypothesis predicts that such a change in load should have no effect on final position accuracy.3. Under normal conditions no final position error developed when the viscous friction was increased. A small overshoot occurred when the viscous friction was decreased.4. The electromyogram recorded from surface electrodes over the belly of flexor pollicis longus in the forearm revealed an increase in activity in response to an increase in viscous friction and a decrease in activity when the viscous friction was reduced.5. When the joint and cutaneous afferents from the thumb were anaesthetized, the e.m.g. response to a change in viscous friction was severely attenuated and consistent final position errors developed.6. Even though the compensatory open‐loop muscle properties went some way towards maintaining accuracy, the change in final position error that occurred as a result of thumb anaesthesia correlated well (r = 0·84) with the amount of muscle e.m.g. response that was lost.7. The latency of the e.m.g. response to a change in viscous friction was compared to that of a voluntary response by asking the subject to push down or let go upon perception of the load change. Approximately the first 100 ms of the e.m.g. response was unaffected by the voluntary intervention of the subject.8. We conclude that the spring hypothesis does not explain human thumb movement. It is argued that the long‐latency stretch reflex machinery is responsible for some automatic compensation for unexpected interference with movement.
Block of some non‐adrenergic inhibitory responses of smooth muscle by a substance from haemolysed erythrocytes
Authors: Bowman Anne , Gillespie J. S. 
Published: December 2014

1. A preparation of haemolysed rat erythrocytes (the haemolysate) blocked the relaxations of both the bovine retractor penis and the rat anococcygeus muscles in response to field stimulation of their non‐adrenergic inhibitory nerves. The effective concentration range was 5‐20 μl./ml. of haemolysate, equivalent to 0·25‐1·0 μl./ml. of blood. The active principle in the haemolysate was a non‐dialysable, heat‐labile material of molecular weight between 50,000 and 100,000 daltons. If, as appeared probable, the active component of the haemolysate was oxyhaemoglobin, its effective blocking concentration was 0·5‐2 μM.2. Haemolysate (5‐20 μl./ml.) also blocked the relaxation of both the bovine retractor penis and the rat anococcygeus to the inhibitory factor extracted from the bovine retractor penis, an observation supporting the possibility that this inhibitory factor may be the transmitter released by the inhibitory nerves in these tissues. In the bovine retractor penis, haemolysate was also effective in blocking relaxations in response to sodium nitroprusside, but relaxations produced by prostaglandin E1 or isobutylmethylxanthine were unchanged or only slightly reduced.3. In contrast, in the taenia of the guinea‐pig caecum, haemolysate did not block the non‐adrenergic inhibitory response to field stimulation, nor the relaxation produced by ATP, although it did block the relaxation produced by the inhibitory factor.4. In spiral strips of isolated rabbit aorta, haemolysate (10 μl./ml.) increased the contraction produced by noradrenaline and blocked the relaxation produced by the inhibitory factor. These were shown to be independent effects.5. Apamin, which blocked the relaxation of the taenia of the guinea‐pig caecum elicited by either ATP or field stimulation of its non‐adrenergic nerves, was without effect on relaxations of the bovine retractor penis or rat anococcygeus muscles in response to field stimulation of inhibitory nerves or to inhibitory factor.6. These differences in the blocking effects of apamin and haemolysate suggest either that the transmitter in the bovine retractor penis and rat anococcygeus differs from that in the guinea‐pig taenia, or, if the transmitter is the same, then its mechanism of action differs.
Neural encoding of input transients investigated by intracellular injection of ramp currents in cat α‐motoneurones
Authors: Baldissera F. , Campadelli Paola , Piccinelli L. 
Published: December 2014

1. Input—output relations were analysed in spinal α‐motoneurones during current transients reaching a steady level after a linear growth of different slopes. The motoneurone output considered in the analysis was the instantaneous frequency of the cell discharge.2. In all motoneurones firing frequency during the ramp exceeded that of the final steady level and it was related to the velocity of rise of the current. In the majority of motoneurones the instantaneous frequency grew during the ramp stimulus, as if it were dependent on current intensity as well as on its rate of rise. Only in a few cells was firing frequency constant over the first two interspike intervals during the ramp, as would be expected if this response depended solely on the rate of rise.3. Frequency—velocity (f/v) plots for different rates of rise of the injected current showed a linear relation for each interspike interval. Presence or absence of an intensity component was revealed in these plots by divergence or, respectively, overlapping of the f/v relations for the first and second intervals. Divergence was eliminated by subtraction of the estimated intensity component. The slope of the f/v relation for the first interval did not change significantly after subtraction of the intensity component and was taken as an index of the dynamic sensitivity of the motoneurones. The slope of the f/v relation varied greatly (from 47 to 330 impulses s−1. (nA ms−1)−1) in the population examined and was higher in motoneurones with a long‐lasting afterhyperpolarization (a.h.p.) than in those where it was short‐lasting.4. It is proposed that the ability of the motoneurones to encode both the steady level and the rate of change of input signals depends on the conductance changes responsible for the a.h.p. and their accumulation. A positive correlation was found between the size of the a.h.p. potassium current, estimated as a.h.p. peak voltage/cell input resistance, and the slope of the f/v relation for the first interval.
Effects of ATP or phosphate on passive rubidium fluxes mediated by Na‐K‐ATPase reconstituted into phospholipid vesicles
Authors: Karlish S. J. D. , Stein W. D. 
Published: December 2014

1. The passive Rb fluxes mediated by the Na—K pump in reconstituted vesicles, described by Karlish & Stein (1982), are affected by ATP or by phosphate acting separately.2. Rb—Rb exchange through inside‐out pumps is stimulated by ATP at low concentrations and is inhibited at high concentrations. There are mutual effects of Rb at cytoplasmic sites and ATP. The higher is the Rb concentration, the greater is the degree of stimulation and the less is the inhibition of exchange by ATP, and the higher are the concentrations of ATP required to produce effects. ATP stimulates Rb—Rb exchange maximally by about 5‐fold.3. There are similar effects of ATP on zero‐trans net Rb uptake through inside‐out pumps. However, much lower degrees of stimulation and greater inhibition of the net flux by ATP are observed, and much lower concentrations of ATP are required for these effects, by comparison with those on Rb—Rb exchange.4. Rb uptake on inside‐out pumps in Na‐loaded vesicles shows only inhibition by ATP.5. Phosphate effects require the presence of Mg0 ions. At low Mg0 concentrations (up to 100 μM) phosphate moderately stimulates Rb uptake into Rb‐free or Rb‐loaded vesicles (about 50%), but has no effect on Rb uptake into Na‐loaded vesicles. At millimolar concentrations of Mg0 ions, phosphate strongly inhibits the Rb uptake into Rb‐free or Na‐loaded vesicles but has no effect on Rb uptake into Rb‐loaded vesicles.6. The separate effects of ATP and of phosphate are explained in terms of the model proposed by Karlish & Stein (1982), modified to take into account stimulation of the conformational transition E2(Rb)occ → E1 Rb by ATP, and stimulation of the conformational transition E2(Rb)occ → E2 Rb by phosphate due to phosphorylation of the protein.