bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered somatosensory receptive fields in hamster colliculus after infraorbital nerve section and xylocaine injection.
Authors: Jacquin M F , Mooney R D , Rhoades R W
Published: December 2014

The effects of acute infraorbital (i.o.) nerve section upon the responses of somatosensory cells in the rostral part of the deep layers of the hamster's superior colliculus were studied using standard extracellular single‐unit recording and receptive field mapping techniques. In nine animals a given cell's receptive field was determined both before and after i.o. nerve section and, in all cases, new areas of sensitivity were unmasked within 15 min after the nerve was cut. In a given electrode penetration where the i.o. nerve was sectioned (n = 13), somatosensory cells recorded after the nerve was cut, as the electrode was being withdrawn from the colliculus, exhibited receptive fields considerably different from those of somatosensory cells isolated during the descent of the recording electrode. Seventeen deep‐layer somatosensory cells (in eight hamsters) were tested before and after subcutaneous injections of xylocaine into their receptive fields. This manipulation unmasked new areas of cutaneous sensitivity for sixteen units. Of these, the new receptive fields of nine cells disappeared as sensitivity in the original receptive field returned; five ultimately retained both the new and old receptive fields; in two instances, sensitivity in the original receptive field never returned over the 3 h of testing. Control experiments (n = 7) demonstrated that the changes observed did not result from spontaneous alterations in receptive field borders, changes induced by variations in the level of general anaesthesia, or non‐specific trauma associated with the xylocaine injections or the surgery required to expose the i.o. nerve.
Sensory physiology, anatomy and immunohistochemistry of Rohon‐Beard neurones in embryos of Xenopus laevis.
Authors: Clarke J D , Hayes B P , Hunt S P , Roberts A
Published: December 2014

Rohon‐Beard neurones show substance P‐like immunoactivity in their somas and in their centrally projecting axons. Peripherally, the morphology of their free nerve endings within the trunk skin has been shown using horseradish peroxidase staining. The excitation of Rohon‐Beard neurones by natural and electrical stimulation of the skin has been examined using intracellular micro‐electrodes in the late embryo of Xenopus laevis. Rohon‐Beard cells are sensitive to transient, local indentation of the trunk skin, responding with one or a few impulses. They adapt rapidly to repeated stimulation. They can also be excited by a brief current pulse to the skin. They are not sensitive to slow indentation of the skin, nor are they excited by epithelial action potentials. The responses to skin stimulation are not abolished by a Ringer solution containing 12 mM‐Mg2+ and only 0.5 mM‐Ca2+. Intracellularly evoked action potentials in single Rohon‐Beard cells are sometimes sufficient to evoke sustained episodes of fictive swimming. The results indicate that Rohon‐Beard cells are responsible for detecting light touch stimuli to the embryo's body and for initiating swimming in response to this stimulus.
The contrasting stretch reflex responses of the long and short flexor muscles of the human thumb.
Authors: Matthews P B
Published: December 2014

The electromyographic activity of flexors pollicis longus and brevis (with its synergists) has been compared on forcibly extending the thumb at various velocities with the muscles initially contracting. Both muscles gave short‐ and long‐latency responses, but these differed in their relative magnitude with short‐latency responses being better developed for the short flexor. With jerk‐type stimuli both muscles gave short‐latency responses with the expected slight difference in latency due to their different position in the arm. That of the long flexor was sometimes immediately followed by a long‐latency response to the same stimulus. With slower displacements the short flexor regularly showed much more short‐latency response than did the long flexor. The ensuing long‐latency activity of the short flexor was normally appreciably less than that of the long flexor. However, since the short‐latency response may be presumed to leave the motoneurones refractory it cannot be definitively concluded from this that acting in isolation long‐latency pathways would be less potent for the short flexor, though this seems quite likely to be so. In some cases the first reflex activity occurred nearly synchronously for the two muscles in spite of their different separation from the spinal cord. That for the more distal short flexor was a short‐latency response, whereas that for the more proximal long flexor was a long‐latency response. The findings conflict with the provisional generalization that for muscles of the primate hand short‐latency responses have been regularly supplanted by long‐latency responses. They also provide the basis for a teleological argument against the view that the long‐latency response is mediated transcortically.
Proprioceptors and normal tremor.
Authors: Burne J A , Lippold O C , Pryor M
Published: December 2014

The tremor of the hand, rotating about the wrist joint, was measured using an accelerometer, and groups of muscle action potentials were simultaneously recorded from the wrist extensor muscles using surface electrodes. The accelerometer signal and the rectified, demodulated electromyogram were submitted to Fourier analysis in order to quantify the tremor in terms of its frequency components and the amplitudes of those components. The amplitudes of the 8‐12 Hz peak in the frequency spectrum obtained from muscle electrical activity were compared (a) when the hand was held raised against gravity (i.e. the contraction was isotonic) with (b) when it was held raised, with the same force and in the same position against a rigid bar (i.e. the contraction was isometric). In the isotonic condition (a) a prominent 8‐12 Hz peak was observed in the spectrum. In the isometric condition (b) the peak was small or absent. The conclusion is drawn that the grouping (synchronization) of motor unit action potentials underlying tremor cannot be due to any process in the central nervous system generating them and they depend on cyclic alterations in muscle length activating proprioceptors.
Sodium pump stoicheiometry determined by simultaneous measurements of sodium efflux and membrane current in barnacle.
Authors: Lederer W J , Nelson M T
Published: December 2014

Ouabain‐sensitive Na efflux, membrane potential and membrane current were measured in single, perfused muscle cells taken from the giant barnacle, Balanus nubilus. This preparation permits control of the intracellular and extracellular solution composition as well as control of the membrane potential while measuring ion fluxes across the plasma membrane. The addition of ouabain (10(‐4) M) to the extracellular solution produces a rapid depolarization of membrane potential (1‐4 mV) and a simultaneous and proportional reduction of Na efflux (10‐40 pmol/s). Ouabain‐induced changes in membrane potential or Na efflux do not depend on the presence of extracellular Na. Under voltage control, the application of ouabain (10(‐4) M) produces a rapid monotonic fall in outward current (1‐3 microA) and a simultaneous fall in Na efflux (10‐40 pmol/s). The fraction of ouabain‐dependent Na efflux that appears as outward current is constant in any given preparation as the Na‐pump turnover rate varies. Over a limited range, changes in membrane potential do not affect ouabain‐sensitive Na efflux. The ouabain‐sensitive Na efflux and membrane current are not altered by the presence of 50 mM‐internal tetraethylammonium (TEA) ions. We conclude that the Na pump is electrogenic in barnacle muscle and that 49 +/‐ 10% of the extruded Na+ leaves the intracellular compartment as uncompensated charge. We find that the transport stoicheiometry of Na:K, calculated from the ouabain‐dependent changes in membrane current and Na efflux, is between 3:2 and slightly more than 2:1.
Non‐linear summation of tension in motor units of toad slow muscle.
Authors: Morgan D L , Proske U
Published: December 2014

Tension developed by single motor units and bundles of motor units has been recorded from the slow, non‐twitch portion of the iliofibularis muscle of the toad Bufo marinus. Evidence was sought for the presence of individual muscle fibres within a motor unit which remained less than fully activated when the axon was maximally stimulated, i.e. at a rate and duration sufficient to produce maximum tension. When two motor units were stimulated separately and together, one at a low rate and the other at a maximal rate, the tension recorded on combined stimulation was greater than the sum of individual tensions, i.e. combined stimulation acted to 'facilitate' tension in a proportion of fibres. Adding the anticholinesterase eserine to the solution bathing the muscle produced a large increase in individual motor unit tensions but a rather smaller increase during combined stimulation of several axons. This suggested that in normal solution, maximally stimulating a single axon left many muscle fibres less than fully activated. When the local anaesthetic lignocaine was added to the bathing solution, tension in response to nerve stimulation fell, presumably because of impulse blockade in small terminal branches of the axon. However tension fell more steeply for single motor units than for combinations of motor units, again, we propose, because single motor units contain a larger fraction of incompletely activated fibres whose tension output depends critically on the level of activation. Overlap between two motor units is a measure of the proportion of fibres innervated by both axons. When overlap was measured over a range of different muscle lengths and using contractions of different durations, evidence was obtained in support of the notion that tension output of some muscle fibres was less than maximum not only because the fibre received too sparse an innervation to achieve a sufficient over‐all level of depolarization but because they had been non‐uniformly activated, leading to internal motion within the fibre and a consequent further drop in tension.
Circulatory and osmoregulatory effects of angiotensin II perfusion of the third ventricle in a bird with salt glands.
Authors: Gerstberger R , Gray D A , Simon E
Published: December 2014

In Pekin ducks adapted to salt water, 1Asp ‐ 5Val ‐angiotensin II, 1Asp ‐ 5Ile ‐angiotensin II and 1Asp ‐ 5Ile ‐tetradecapeptide were applied intracerebroventricularly (I.C.V.) during steady‐state conditions evoked by continuous intravenous loading with 200 mosmol kg‐1 saline. Each of the angiotensin II (AII) analogues caused a dose‐dependent antidiuresis with a concomitant rise in urine osmolality and electrolyte concentration. Antidiuresis was linearly correlated with plasma arginine vasotocin (AVT). The elevation of plasma AVT occurred rapidly during I.C.V. stimulation with AII and declined exponentially to the pre‐stimulation level. Under conditions of salt loading with 1000 mosmol kg‐1 saline in which the ducks excreted the salt and water by their supraorbital salt glands, AII applied I.C.V. in a concentration of 1 nmol ml‐1, inhibited the NaCl excretion via the salt glands. Arterial blood pressure and heart rate increased after I.C.V. microperfusion with 1 nmol ml‐1 AII. This was not due to leakage of I.C.V. AII into the circulation because systemic application of AII required a 100‐fold higher dose to elicit similar effects. Respiration rate remained constant. Systemically applied AVT which produced plasma levels similar to, or greater than, those caused by centrally acting AII resulted in the same antidiuretic responses but did not mimic the circulatory effects of I.C.V. AII. Specific AVT antiserum, injected intravenously, totally suppressed the renal response to I.C.V. AII and reduced the rise in blood pressure and heart rate by more than 50%. The anterior part of the third ventricle was more sensitive than the posterior part in eliciting the antidiuretic responses to I.C.V. applied AII. The particular combination of effects on renal excretion, salt gland secretion and cardiovascular function of centrally applied AII in the duck supports the idea that AII plays a major role as a central modulator of volume homeostasis.
Braking of fast and accurate elbow flexions in the monkey.
Authors: Flament D , Hore J , Vilis T
Published: December 2014

The processes responsible for braking fast and accurate elbow movements were studied in the monkey. The movements studied were made over different amplitudes and against different inertias . All were made to the same end position. Only fast movements that showed the typical biphasic or triphasic pattern of activity in agonists and antagonists were analysed in detail. For movements made over different amplitudes and at different velocities there was symmetry between the acceleration and deceleration phases of the movements. For movements of the same amplitude performed at different velocities there was a direct linear relation between peak velocity and both the peak acceleration (and integrated agonist burst) and peak deceleration (and integrated antagonist burst). The slopes of these relations and their intercept with the peak velocity axis were a function of movement amplitude. This was such that for large and small movements of the same peak velocity and the same end position (i) peak acceleration and phasic agonist activity were larger for the small movements and (ii) peak deceleration and phasic antagonist activity were larger for the small movements. The slope of these relations and the symmetry between acceleration and deceleration were not affected by the addition of an inertial load to the handle held by the monkey. The results indicate that fast and accurate elbow movements in the monkey are braked by antagonist activity that is centrally programmed. As all movements were made to the same end position, the larger antagonist burst in small movements, made at the same peak velocity as large movements, cannot be due to differences in the viscoelastic contribution to braking (cf. Marsden, Obeso & Rothwell , 1983).(ABSTRACT TRUNCATED AT 250 WORDS)
Inward rectifier current noise in frog skeletal muscle.
Authors: DeCoursey T E , Dempster J , Hutter O F
Published: December 2014

Inwardly rectifying K+ currents were studied in cut muscle fibres from frogs using the Vaseline‐gap voltage‐clamp method. Both faces of the membrane were exposed to 120 mM‐K+ methylsulphate solution. At small negative potentials, ‐10 and ‐21 mV, the current noise spectrum, after subtraction of a control spectrum at the zero current potential, could be fitted by a Lorentzian spectral component, usually with an additional 1/f component, where f is the frequency. At more negative potentials the 1/f component predominated. The zero frequency amplitude of the Lorentzian averaged 2.6 X 10(‐24) A2 Hz‐1 at ‐10 mV and 4.6 X 10(‐24) A2 Hz‐1 at ‐21 mV, with a mean half‐power frequency, fc, of 34 Hz and 45 Hz, respectively. The time constant of the K+ current activation upon hyperpolarization agrees with that calculated from fc, and the Lorentzian disappears upon replacement of external K+ by tetraethylammonium (TEA+) or Rb+. Thus, the Lorentzian component appears to be ascribable to fluctuations originating in the inwardly rectifying mechanism. The noise spectra and macroscopic currents were interpreted by assuming that the inwardly rectifying K+ conductance is proportional to the product of two parameters: ps representing the state of the mechanism that gives rise to the observable macroscopic current relaxations and to the current fluctuations resulting in the observed Lorentzian spectra, and pf describing the instantaneous rectification of the single‐channel conductance. Alternatively, pf may represent another mechanism in series with ps, but which fluctuates too rapidly to measure. Using this model the limiting single‐channel conductance, gamma, was found to be approximately 9 pS. The corresponding specific density of channels is about 1 micron‐2, assuming uniform distribution over all regions of the membrane. A preliminary value for gamma ( DeCoursey & Hutter , 1982) was derived without consideration of instantaneous rectification. Systematic errors in these results due to voltage decrement in the T‐tubules are evaluated in an Appendix, and are found to be tolerably small in the voltage range studied.
Pulmonary surfactant: hydrophobic nature of the mucosal surface of the human amnion.
Authors: Cotton D B , Hills B A
Published: December 2014

The contact angle has been measured for a drop of saline placed upon the rinsed mucosal surface of the amnion in eleven human placental membranes obtained from normal births at full term. The contact angle averaged 70 degrees, indicating a hydrophobic surface comparable with graphite (86 degrees), polyethylene (94 degrees) or oxyntic tissue (85 degrees) which is also exposed to endogenous surface‐active phospholipids in vivo. By comparison, four pre‐term placentas with an average gestation period of 29.5 weeks gave a mean contact angle of 32 degrees, indicating that hydrophobicity of the placenta increases with maturity (41 weeks) and might well be imparted by adsorbed surfactants present in amniotic fluid and known to render other surfaces hydrophobic. Since the mucosal epithelium of the amnion is exposed to the same surfactants in the same physical state as the fetal alveolar wall, the above results imply that this surface may also be hydrophobic, as indicated in the adult lung by other studies. The concept of surfactant directly adsorbed to the pulmonary tissue surfaces is discussed in connexion with its possible functional advantages in 'de‐watering' the lung at birth, maintaining homeostasis by water repellency , releasing airway surfaces and lymph ducts glued by protein and lubricating tissue respiratory movement.
Activity patterns and osmosensitivity of rat supraoptic neurones in perfused hypothalamic explants.
Authors: Bourque C W , Renaud L P
Published: December 2014

Extracellular recordings were obtained in vitro from supraoptic neurones in an explant of rat hypothalamus maintained viable through intravascular perfusion with artificial media. The spontaneous activity observed from 64% of cells included continuously active neurones (mean frequency 3.2 +/‐ 0.8 Hz) located throughout the nucleus, and phasically active neurones (8.6 +/‐ 0.6 Hz) located predominantly in the caudal half of the nucleus. Supraoptic neurones displayed antidromic activation (latency range 6.5‐18.2 ms) following stimulation of the pituitary stalk and orthodromic excitatory or inhibitory responses following stimulation in the anteroventral third ventricular (AV3V) region. Synaptic responses were reversibly abolished during perfusion with media containing 12 mM‐Mg2+. A 15‐40 mosmol/l increase in the osmotic pressure of the perfusion media, through addition of NaCl, sucrose or mannitol, prompted nineteen of twenty‐three cells to increase their discharge frequency. The patterns of response included the induction or simple increase in continuous firing frequency, the induction or enhancement of phasic or bursting activity and a change from continuous to phasic activity. Similar responses to an osmotic stimulus were obtained from thirteen of twenty‐one supraoptic neurones, including two phasic neurones, where synaptic activity had been abolished during perfusion with 12 mM‐Mg2+. Osmosensitivity appeared to be selective for supraoptic cells; no significant change in firing frequency was observed from any of six cells recorded in the lateral hypothalamus or thirteen cells recorded in the medial hypothalamus during exposure to a change in osmotic pressure of +20 to +40 mosmol/l, using either control media (seven cells) or media containing 12 mM‐Mg2+ (twelve cells). These observations indicate that supraoptic neurones maintained in vitro can display spontaneous, antidromie , orthodromic and osmotically induced activity patterns identical to those observed with in vivo recordings. The persistence of a reduced osmosensitivity among supraoptic neurones in the absence of synaptic transmission indicates that although these cells can function as osmoreceptors, their osmosensitivity may be enhanced through synaptic input from adjacent neurones, possibly located in the AV3V area. The presence of phasic activity among supraoptic neurones maintained in media where synaptic transmission has been abolished suggests that the mechanisms responsible for such activity patterns are endogenous membrane properties of a subpopulation of supraoptic neurones.
Interaction between areas of the central nervous system in the control of water intake and arterial pressure in rats.
Authors: Camargo L A , Menani J V , Saad W A , Saad W A
Published: December 2014

Water intake induced by injection of 0.2 M‐NaCl into the lateral preoptic area was increased by the injection of angiotensin II into the subfornical organ of rats. The injection of hypertonic saline solution into the subfornical organ increased water intake. However, the increase was lower than when the solution was injected into the lateral preoptic area. The injection of 4 micrograms angiotensin II into the lateral preoptic area further augmented this effect. Injection of angiotensin II into the subfornical organ caused a rise in blood pressure which preceded the thirst‐inducing effect. The injection of 0.2 M‐NaCl into the subfornical organ caused no changes in blood pressure, whereas the injection of angiotensin II into the lateral preoptic area caused some increase. Dehydration of the lateral preoptic area by means of 0.2 M‐NaCl in combination with intravenous infusion of angiotensin II caused a summation of effects in terms of the water intake, without changing cardiovascular alterations induced by the infusion of angiotensin II. A summation of effects in the water intake, but not in blood pressure, was also observed when 0.5 M‐NaCl was infused intravenously in combination with the injection of angiotensin II into subfornical organ and into the lateral preoptic area. The results indicate that there are interactions between the subfornical organ and lateral preoptic area in the regulation of cardiovascular and thirst mechanisms.
Mechanoreceptor pathways from the distal colon to the autonomic nervous system in the guinea‐pig.
Authors: King B F , Szurszewski J H
Published: December 2014

Electrophysiological and histological techniques were used to trace sensory pathways for stretch mechanoreceptor fibres from the distal colon to dorsal root ganglia. Extracellular and intracellular recording techniques revealed sensory pathways for mechanoreceptors to the prevertebral sympathetic ganglia but no further centrally. Histological studies involving the retrograde transport of horseradish peroxidase revealed sensory pathways from the distal colon to the spinal cord, mainly to the level of the second lumbar vertebra. Few (less than 2000) fibres were involved; their perikarya were small (ca. 25 micron). Sensory perikarya in spinal ganglia in the guinea‐pig could be categorized into two populations, F and H cells, after a previously defined nomenclature for murine spinal ganglion cells. F and H cells were distinguished initially by their times to decay by 50% of the action potential. H cells took three times as long to repolarize. F and H cells were distinguished further by their electrical properties including membrane potential, input resistance and amplitude and duration of the after‐potential following the action potential. Both F and H cells showed unusual time‐dependent rectification following either depolarizing or hyperpolarizing current pulses. Threshold currents to show rectification were different for F and H cells. When taken in conjunction with conduction velocities, the electrophysiological evidence may assist in identifying sensory neurones. For example, H cells appeared to have slow conducting (C fibre) axons. From the lack of electrophysiological evidence and limited histological support for major central sensory pathways, it is concluded that stretch mechanoreceptor information from the colon of the guinea‐pig is referred mainly to the prevertebral ganglia with minimal involvement of the spinal cord.
Restoration of function in external intercostal motoneurones of the cat following partial central deafferentation.
Authors: Kirkwood P A , Sears T A , Westgaard R H
Published: December 2014

The activity of external intercostal motoneurones in the cat was studied under anaesthesia and paralysis before and after partial central deafferentation caused by single or double ipsilateral hemisections of the thoracic spinal cord. The normal efferent inspiratory discharges recorded from external intercostal nerve filaments caudal to the upper lesion were greatly reduced acutely, but activity of approximately normal intensity and phase at eupneoic levels of CO2 was restored within a few days and remained at similar levels for up to two years. The patterns of the restored activity were abnormal, with more discharges of alpha‐motoneutrones during expiration than normal and a stronger modulation of the discharges by the respiratory pump than normal. A common abnormal component of the restored activity was a tonic discharge in hypocapnic apnoea, often modulated by the respiratory pump. This activity was never seen in normal animals or in those with acute lesions under similar conditions of anaesthesia. Synchronization of the discharges of alpha‐motoneurones caudal to the upper lesion was studied by constructing cross‐correlation histograms between paired groups of motoneurones, each group being represented by the discharges in one filament. Synchronization was stronger than normal, usually extending over a time course of +/‐ 20 to +/‐ 50 ms (broad‐peak synchronization). This synchronization was particularly strong for the discharges in hypocapnic apnoea. We conclude that the restored activity was derived in large part from abnormal tonic (non‐respiratory‐phased) inputs, partly proprioceptive in origin, probably involving spinal cord interneurones with abnormally synchronized discharges. This conclusion is supported by intracellular measurements including respiratory drive potentials, synaptic noise and average common excitation potentials.
The effects of valinomycin on ion movements across the sarcoplasmic reticulum in frog muscle.
Authors: Kitazawa T , Somlyo A P , Somlyo A V
Published: December 2014

The effects of valinomycin on the elemental composition and the fractional volume of the terminal cisternae (t.c.) of the sarcoplasmic reticulum (s.r.) were determined in rapidly frozen frog semitendinosus muscles. The concentrations of valinomycin used for the electron probe studies (5 microM) had no effect on tetanus tension or t.c. volume (2.% of fibre volume). Mitochondria were markedly swollen and their K content was significantly increased in both the resting and the tetanized valinomycin‐treated muscles. Valinomycin had no effect on the concentration of Na, Mg, P, Cl, K and Ca in the t.c. of resting muscles. In untreated, tetanized muscles, Ca2+ release was accompanied by the uptake of K and Mg into the t.c. in an amount that was significantly less than the positive charge removed through Ca2+ release, confirming previous observations showing an apparent charge deficit (Somlyo, Gonzalez‐Serratos, Shuman, McClellan & Somlyo, 1981). Valinomycin abolished the apparent charge deficit: in tetanized, valinomycin‐treated muscles, the uptake of K into the t.c. was significantly (P less than 0.001) greater than in the untreated muscles and Mg uptake also remained highly significant. It is suggested that Ca2+ release from activated muscle is an electrogenic process and that the K+ conductance of the s.r. in untreated frog muscles is insufficient to allow charge neutralization of the Ca2+ current during release. The increase in K+ permeability caused by valinomycin permits the greater counter movement of K+ under the combined influence of the electrical potential generated by outward Ca2+ movement and the acidic cation binding proteins in the lumen of the s.r. The results are consistent with the proposal (Somlyo et al. 1981) that in normal frog muscles not treated with valinomycin, the apparent positive charge deficit observed after a tetanus reflects the movement of protons and, possibly, organic cations.
Characteristics of membrane channels induced by acetylcholine at frog muscle‐tendon junctions.
Authors: Miledi R , Reiser G , Uchitel O D
Published: December 2014

The membrane at the tendinous ends of frog muscle fibres has acetylcholine (ACh) receptors that are blocked by alpha‐bungarotoxin. The properties of ACh‐activated channels in the myotendinous region were investigated by noise analysis. These channels displayed the same characteristics in normal, denervated and reinnervated muscles. The mean lifetime and conductance of ACh‐induced channels at the myotendinous junction resembled those of channels at the normal neuromuscular junction. Both channels opened with a lifetime shorter than that of extrajunctional receptors. Channels of short lifetime could be detected at distances of several hundred micrometres from the tendon junction. The similarity of ACh‐activated channels at neuromuscular and myotendon junctions was found both in the fast, 'singly' innervated sartorius and cutaneous pectoris muscle and in the intermediate, multiply innervated submaxillaris muscle.
Synaptic and antidromic potentials of visceral neurones in ganglia of the lumbar sympathetic chain of the cat.
Authors: Hartman D A , Krier J
Published: December 2014

Intracellular recordings were obtained in vitro from two hundred and twenty post‐ganglionic neurones of the fourth and fifth lumbar paravertebral ganglia of cats. Thirty‐seven percent of neurones tested evoked antidromic responses during electrical stimulation of post‐ganglionic fibres in the inferior lumbar splanchnic nerves. Twenty‐seven percent of neurones tested evoked antidromic responses during electrical stimulation of post‐ganglionic fibres in the lumbar sympathetic chain. Twenty‐four percent of neurones tested evoked convergent antidromic responses during electrical stimulation of post‐ganglionic fibres in separate inferior lumbar splanchnic nerves or lumbar sympathetic chain, and by inferior lumbar splanchnic nerves and lumbar sympathetic chain. Eighty‐six percent of paravertebral post‐ganglionic fibres which project to the inferior lumbar splanchnic nerves or lumbar sympathetic chain were composed of B fibres with maximal conduction velocities ranging from above 2.0 to 16.0 m/s. Fourteen percent of post‐ganglionic fibres were composed of C fibres with maximal conduction velocities ranging from 0.2 to 2.0 m/s. Synaptic responses of neurones were recorded intracellularly during electrical stimulation of preganglionic fibres in inferior lumbar splanchnic nerves, lumbar white rami communicantes and lumbar sympathetic chain located one to three segments above the fourth and fifth lumbar ganglia and one to two segments below. Synaptic responses consisting of excitatory post‐synaptic potentials and action potentials were mediated via nicotinic receptors. Twenty‐seven percent of neurones tested received synaptic input from only one or two segments of the lumbar sympathetic chain. Seventy‐three percent of neurones tested received convergent synaptic input from one or two segments of the lumbar sympathetic chain, lumbar white rami communicantes and inferior lumbar splanchnic nerves. It is concluded that central preganglionic fibres which project to inferior lumbar splanchnic nerves also project to the lumbar sympathetic chain to innervate neurones in the L4 and L5 ganglia. Synaptic responses of neurones during electrical stimulation of preganglionic fibres in the lumbar sympathetic chain and in the inferior lumbar splanchnic nerves were reduced in a chronic isolated segment of the sympathetic chain devoid of central preganglionic inputs. It is concluded that synaptic responses elicited in neurones during electrical stimulation of inferior lumbar splanchnic nerves and lumbar sympathetic chain were mediated in part via collaterals of central preganglionic axons and in part via axons whose cell bodies were located in the periphery.(ABSTRACT TRUNCATED AT 400 WORDS)
The pattern of breathing in man in response to sine waves of alveolar carbon dioxide and hypoxia.
Authors: Cunningham D J , Robbins P A
Published: December 2014

Sine waves of alveolar CO2 at constant high alveolar O2, and sine waves of alveolar hypoxia (1/(PA, O2 ‐C) where C congruent to 32 torr) at constant alveolar CO2 have been administered to three subjects in each case. Six different periods of the sine waves were studied, ranging between 900 and 30 s for the CO2 sine waves and 300 and 20 s for the hypoxic sine waves. The sinusoidal variations in inspiratory and expiratory volumes (VT, I, VT, E), durations (TI, TE) and mean flows (vI, vE) produced by these manoeuvres were calculated, and the results analysed from the phase shifts of the responses. For the CO2 sine‐wave results, the peak in the TI oscillation generally appeared after the minima for VT, I and vI, but before their maxima. The peak in the TE oscillation was variable. For the hypoxic sine‐wave results, the peak in the TI oscillation showed no over‐all tendency to lead or lag the peaks of VT, I and vI. The peak in the TE oscillation generally appeared after the maxima for VT, E and vE but before their minima. For the CO2 sine‐wave results, expiratory mean flow led inspiratory mean flow, with the volumes showing no significant difference. For the hypoxic sine‐wave results expiratory volumes and mean flows led inspiratory volumes and mean flows. The results are discussed in relation to the transient responses of the components of breathing pattern obtained from other perturbations of chemical drive.
Supersensitivity of the rabbit iris sphincter muscle induced by trigeminal denervation: the role of substance P.
Authors: Fujiwara M , Hayashi H , Muramatsu I , Ueda N
Published: December 2014

The rabbit left ophthalmic nerve (first branch of the left trigeminal nerve) was cut at the intracranial, peripheral side of the trigeminal ganglion and the effects of denervation were examined using iris sphincter muscle preparations isolated from the left and right eye, as denervated and control innervated preparations, respectively. Electrical transmural stimulation produced a substance P‐operated contraction, in addition to a cholinergic one, in the preparation isolated from the right control eye. The former response was abolished in the preparation isolated from the left denervated eye, thereby indicating that the trigeminal, substance P nerve ipsilaterally innervates the iris sphincter muscle. Exogenously applied carbachol and substance P produced concentration‐dependent contractions in preparations isolated from either eye. Supersensitivity characterized by a decrease in median effective concentration (EC50) values and an increase in maximal response was observed in the responses to both agents of the left denervated preparation. Such supersensitivity developed slowly after trigeminal denervation and 3 weeks was required for full development. Exogenously applied KCl produced substance P‐operated and direct muscle contractions in the right control preparations. In the left denervated preparations, the substance P‐operated contraction was either markedly attenuated or abolished, while the direct muscle‐related contraction was enhanced after trigeminal denervation. The length of the left denervated preparation was longer than that of the right control preparation, and the resting tensions required to produce maximal carbachol contraction shifted to lower values. These physical changes of the iris sphincter muscle developed within 5 days after trigeminal denervation. In the non‐denervated preparation treated with capsaicin in vitro, electrical transmural stimulation and KCl failed to produce the substance P‐related contraction. However, supersensitivity to neither exogenously applied substance P, carbachol and KCl nor physical changes were observed in the capsaicin‐treated preparation. These results suggest that trigeminal, substance P‐related nerves tonically and ipsilaterally innervate the rabbit iris sphincter muscle and that the denervation results in non‐specific supersensitivity. These findings are essentially the same as those observed in various types of smooth muscles after autonomic denervation.
Effect of ions on retinal rods from Bufo marinus.
Authors: Hodgkin A L , McNaughton P A , Nunn B J , Yau K W
Published: December 2014

The effect of ions on the light‐sensitive current of isolated retinal rods from the toad Bufo marinus was studied by sucking the inner segment into a tightly fitting pipette. The outer segment projected into flowing solution whose composition could be changed rapidly. Reducing the external Na concentration, [Na]o, round the outer segment caused rapid and reversible reductions in the light‐sensitive current. With the outer segment in the pipette, reductions of [Na]o round the inner segment had little effect on the light‐sensitive current. The current about 15 s after a change in [Na]o was approximately proportional to [Na]2o. The current decreased in elevated external Ca concentration, [Ca]o, and increased in reduced [Ca]o. Between 10 and 0.5 mM‐external Ca the current 15 s after a change was approximately inversely proportional to [Ca]o. Reducing [Ca]o from 1 mM to 1 microM or less transiently increased the current by about 15‐fold. After a change in [Na]o or [Ca]o the current did not approach its final value monotonically but with a characteristic overshoot or underswing, followed by a slow relaxation of current which may reflect the time course of change in internal Na. Reducing [Na]o from 110 to 70 mM or less prolonged the response to a flash; very long responses were observed in solutions containing Li rather than Na and also in rods that had been returned to Ringer solution after exposure to low Ca. All these effects might be explained if Ca extrusion in exchange for Na determines the reactivation of current after a flash. The rod current was not changed if the ratio [Na]No/[Ca]o was held constant, N being about 2.5. Between 5 mM and 10 microM‐Ca the change in peak current produced by absorption of a single quantum was roughly proportional to the dark current. Responses in the absence of external Na were not normally seen if the solution contained 0.1 mM‐Ca or more. Responses of normal polarity were regularly observed in 0 Na, 0 Ca EGTA solutions containing 1.6 mM‐Mg. Removal of Mg from such solutions gave inverted responses. Other conditions which promote responses of normal and inverted polarity in Na‐free solutions are described briefly. We conclude that Li, Ca, Mg and perhaps K can pass through the light‐sensitive channel. The above results suggest that external Na has two distinct effects: (1) it provides ions to carry inward current, and (2) it keeps the light‐sensitive conductance open by maintaining the internal Ca concentration, [Ca]i, at a low level.
The presynaptic regulation of noradrenaline release differs in mesenteric arteries of the rabbit and guinea‐pig.
Authors: Kuriyama H , Makita Y
Published: December 2014

Prejunctional control mechanisms of neuromuscular transmission in mesenteric arteries of the guinea‐pig and rabbit were compared by examining excitatory junction potentials (e.j.p.s). The various agents used did not modify the membrane potential or resistance of smooth muscle cells of either tissue at the concentrations used in the present experiments. In the rabbit mesenteric artery, 10(‐7) M‐phentolamine and yohimbine had almost no effect on the amplitude of e.j.p.s or on facilitation. In the guinea‐pig mesenteric artery, phentolamine enlarged and yohimbine reduced the amplitude of the first e.j.p. but both agents markedly enlarged the amplitude of e.j.p.s evoked by repetitive perivascular nerve stimulation at frequencies over 0.1 Hz. In the rabbit mesenteric artery, isoprenaline and dibutyryl cyclic AMP inhibited the e.j.p.s and the facilitation evoked by repetitive stimulation, while in the guniea‐pig mesenteric artery, isoprenaline enhanced the amplitude of e.j.p.s and the facilitation process. In the rabbit mesenteric artery, ATP inhibited the amplitude of e.j.p.s with no change in facilitation and adenosine inhibited mainly the facilitation process evoked by repetitive perivascular nerve stimulation. In the guinea‐pig mesenteric artery, these agents had no effect on e.j.p.s or facilitation. In both the rabbit and guinea‐pig, indomethacin enlarged the amplitude and prolonged the duration of e.j.p.s. Prostaglandin E2 and F2 alpha inhibited the amplitude of e.j.p.s. Enlarged amplitudes of the e.j.p.s following pre‐treatment with indomethacin were inhibited by treatment with PGE2 or ATP. In the rabbit mesenteric artery, 8‐phenyltheophylline (an antagonist of P1 subtype of purinergic receptor) had no effect on the e.j.p.s, but these agents did reverse the inhibitory action of 2‐chloroadenosine (an agonist of P1 subtype of purinergic receptor) or adenosine on facilitation of e.j.p.s. Theophylline did not have any direct effect on e.j.p.s nor did it reverse the effects of adenosine or 2‐chloroadenosine. In the rabbit mesenteric artery, ATP and adenyl‐imidophosphate showed much the same potency in inhibiting the amplitude of e.j.p.s. Therefore, the ATP action on nerve terminals is not due to a high energy requiring mechanism. From these results we conclude that the control mechanisms related to noradrenaline (NA) release in nerve terminals differ in the guinea‐pig and rabbit mesenteric arteries.(ABSTRACT TRUNCATED AT 400 WORDS)
Reversal by angiotensins II and III of the effects of converting enzyme inhibition on renal electrolyte excretion in rats.
Authors: Harris P J , Munro J O
Published: December 2014

Experiments were carried out in anaesthetized rats to compare the abilities of angiotensin II (A II) and angiotensin III (A III) to reverse the effects of angiotensin converting enzyme inhibition (Teprotide) on salt and water excretion. In rats infused with Teprotide, significant increases in urine flow and sodium excretion were observed and arterial blood pressure decreased. Addition of A II (10 pmol min‐1) to the Teprotide infusion reduced renal excretion of sodium and water to control values and excretion of potassium to below control. Blood pressure increased to a value significantly higher than that during the control period. In a separate group of rats the natriuretic and diuretic effects of Teprotide were reversed by a similar dose of A III (10 pmol min‐1). A primarily angiotensin‐mediated action is indicated for the renal effects of Teprotide. Although angiotensins II and III appeared to be equipotent in their abilities to reverse the renal responses to Teprotide, A II caused an increase in arterial blood pressure that was not seen with A III. In a third group of rats A II (10 pmol min‐1) was added to the Teprotide infusion and an aortic snare located between the renal arteries was tightened to prevent any increase in left renal perfusion pressure. During this period the rate of sodium excretion from the left kidney was significantly lower than from the right kidney. It is concluded that in the absence of any accompanying 'pressure natriuresis' A II is more potent than A III in its ability to reverse the natriuretic action of Teprotide. The elevation of blood pressure to above control values by a dose of A II only just sufficient to reverse the Teprotide‐induced natriuresis suggests that the concentration of angiotensin in the kidney is higher than in plasma and supports the concept of an intrarenal renin‐angiotensin system. In the rat both A II and A III may affect renal salt and water excretion by a combination of mechanisms involving glomerular, vascular and tubular receptors. The possibility is raised that differential effects of the active angiotensins on these mechanisms may participate in the regulation of sodium excretion.
Indoleamine‐mediated reciprocal modulation of on‐centre and off‐centre ganglion cell activity in the retina of the cat.
Authors: Thier P , Wässle H
Published: December 2014

The effects of applying the indoleamines serotonin (5‐hydroxytryptamine) and 5‐methoxy‐N,N‐dimethyltryptamine (MDT) ionophoretically onto cat retinal ganglion cells were studied in the optically intact eye of the cat. Serotonin suppressed both the spontaneous activity and light‐evoked discharge of on‐centre ganglion cells, regardless of the visual stimulus used; on the other hand, it enhanced the activity of off‐centre ganglion cells. MDT produced the opposite effects, i.e. it enhanced the activity of on‐centre ganglion cells but suppressed that of off‐centre ganglion cells. Much of the effect of serotonin on light‐evoked discharge can be attributed to an alteration of maintained discharge. There was no major difference in the way brisk‐sustained (X) and brisk‐transient (Y) cells responded to the application of serotonin and MDT, although the effects of the indoleamines on brisk‐transient (Y) cells were generally weaker than on brisk‐sustained (X) cells. In view of the fact that the action of serotonin is similar to the action of a gain control system, a possible contribution of indoleamine‐accumulating neurones to gain control in the cat retina is discussed.
Differential effect of nerve injury at birth on the activity pattern of reinnervated slow and fast muscles of the rat.
Authors: Navarrete R , Vrbová G
Published: December 2014

The activity patterns of the reinnervated slow soleus and fast extensor digitorum longus (e.d.l.) muscles were studied in rats during the first 6 months after sciatic nerve crush at birth, using chronic electromyography. When the nerve lesion was inflicted shortly after birth, the recovery of the muscle weight and size was always much less than if the same lesion was inflicted on adult animals. As previously demonstrated, this effect is due to motoneurone and muscle fibre loss. Following reinnervation after a neonatal crush, the soleus muscle recovered its normal tonic activity pattern during postural and spontaneous locomotor activity. By contrast, in the reinnervated e.d.l. muscle, abnormal tonic motor unit activity was recorded during locomotion, in addition to the phasic activity characteristic of the normal muscle. In response to postural reflexes elicited by tilting the animal, tonic motor unit activity was recorded from the reinnervated e.d.l. muscle, whereas the normal muscle was not activated by these stimuli. The aggregate activity recorded from the reinnervated e.d.l. during spontaneous locomotion was about 2‐3 times greater than normal, whereas in the reinnervated soleus no significant change took place. In animals which had their nerves crushed as adults, the activity pattern and aggregate activity of both muscles was similar to normal. The firing pattern of individual motor units from normal and reinnervated muscles was compared. After a neonatal crush, the mean frequency of firing of e.d.l. motor units was significantly lower compared to normal or to that after an adult crush, whereas in soleus no significant change was found. These results indicate that peripheral nerve lesions during early development affect predominantly the development of motoneurones with a phasic, high‐frequency discharge pattern resulting in a shift towards tonic, lower‐frequency motor unit activity.