Laryngeal muscle responses to mechanical displacement of the thyroid cartilage in humans.

Speakers may use laryngeal sensory feedback to adjust vocal fold tension and length before initiating voice. The mechanism for accurately initiating voice at an intended pitch is unknown, given the absence of laryngeal muscle spindles in animals and conflicting findings regarding their existence in humans. Previous reports of rapid changes in voice fundamental frequency following thyroid cartilage displacement suggest that changes in vocal fold length modulate laryngeal muscle contraction in humans. We tested the hypothesis that voice changes resulting from mechanical perturbation are due to rapid responses in the intrinsic laryngeal muscles. Hooked wire electrodes were used to record from the thyroarytenoid, cricothyroid, and sternothyroid muscles along with surface electrodes on the skin overlying the thyroid cartilage in 10 normal adults. Servomotor displacements produced consistent changes in the subjects' vocal fundamental frequency at 70-80 ms, demonstrating changes in vocal fold length and tension. No simultaneous electromyographic responses occurred in the thyroarytenoid or cricothyroid muscles in any subjects. Instead, short-latency responses at 25-40 ms following stimulus onset occurred in the sternothyroid muscles, simultaneous with responses in the surface recordings. The sternothyroid responses may modulate long-latency changes in voice fundamental frequency (approximately 150 ms). The absence of intrinsic laryngeal muscle responses is consistent with a lack of spindles in these muscles. Our results suggest that other sensory receptors, such as mucosal mechanoreceptors, provide feedback for voice control.     

Masseter muscle activity during vestibular stimulation in man

Experimental data report that vestibular afferents affect trigeminal system activity. The aim of this work was to evaluate whether static vestibular stimulation affects the excitability of trigeminal motoneurons in man. In order to assess this, voluntary EMG activity of masseter muscles as well as duration and latency of the early and late components of EMG exteroceptive silent period were evaluated while keeping the subject in vertical position and during 20 degrees static tilt. The experiments were performed on ten adult subjects with no orofacial, neurologic and otologic disorders. Each subject sat on a chair, which kept the complex head-jaw-neck-trunk and the limbs securely fixed, in order to minimize any interference due to the activation of somatosensory and proprioceptive afferents from these districts. The subjects were instructed to contract masseter muscles at 25% of their maximum bite force and the isometric force monitoring was used as visual feedback. Exteroceptive silent period (ESP) of masseter EMG was elicited by electrically stimulating the inferior inter-incisal gum. Results showed that static vestibular stimulation induced asymmetrical responses on voluntary masseter muscle activity, which was reduced to 70.3 +/- 16.1% (mean +/- S.D.) of the control value during ipsilateral tilt and increased to 128.8 +/- 13.0% during contralateral tilt. The duration of the early (ESP1) and late (ESP2) silent periods was also affected: during ipsilateral tilt ESP1 and ESP2 duration increased to 130.0 +/- 3.5% and to 122.1 +/- 2.1% of control, respectively; during contralateral tilt it was reduced to 76.8 +/- 1.2% and to 83.0 +/- 1.7% of control, respectively. On the contrary, changes in latencies were not significant. These data evidenced an asymmetrical effect exerted on trigeminal motor activity by static tilt. Since the influence of all receptors which could be activated by static tilt, except that arising from the macular ones, was minimized in this study, it is likely that the observed effects, induced by static tilt on masseter muscle activity, were of macular origin.     

Activation of thalamic ventroposteriolateral neurons by phrenic nerve afferents in cats and rats.

It has been demonstrated that phrenic nerve afferents project to somatosensory cortex, yet the sensory pathways are still poorly understood. This study investigated the neural responses in the thalamic ventroposteriolateral (VPL) nucleus after phrenic afferent stimulation in cats and rats. Activation of VPL neurons was observed after electrical stimulation of the contralateral phrenic nerve. Direct mechanical stimulation of the diaphragm also elicited increased activity in the same VPL neurons that were activated by electrical stimulation of the phrenic nerve. Some VPL neurons responded to both phrenic afferent stimulation and shoulder probing. In rats, VPL neurons activated by inspiratory occlusion also responded to stimulation on phrenic afferents. These results demonstrate that phrenic afferents can reach the VPL thalamus under physiological conditions and support the hypothesis that the thalamic VPL nucleus functions as a relay for the conduction of proprioceptive information from the diaphragm to the contralateral somatosensory cortex.     

Convergence of synaptic influences of contralateral somatic afferents on interneurons in segmental inhibitory pathways to motoneurons

Convergence of contralateral somatic afferent synaptic influences on segmental inhibitory neurons was investigated by intracellular recording of postsynaptic potentials of -motoneurons in experiments on cats. Excitatory synaptic influences of afferents of the contralateral flexor reflex were shown to converge on interneurons of both segmental inhibitory systems studied: afferents of flexor reflex and group Ia muscle afferents. Interneurons of inhibitory systems are exposed not only to excitatory but also to inhibitory contralateral influences. Contralateral inhibitory PSPs of montoneurons are produced through ipsilateral inhibitory systems; a leading role is played by inhibitory neurons of the flexor reflex system of afferents. Inhibitory neurons of the Ia system as a rule do not make an important contribution to generation of contralateral IPSPs.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 476–484, September–October, 1973.     

Different fusimotor reflexes from the ipsi- and contralateral hind limbs of the cat assessed in the same primary muscle spindle afferents

Experiments were performed in forty-five cats anaesthetized with alpha-chloralose. The aim of the study was to investigate a sample of primary muscle spindle afferents from triceps muscle with respect to their fusimotor reflex control from ipsi- as well as contralateral hind limb. Primary muscle spindle afferents of the triceps surae muscle were recorded from the mean rate of firing and the modulation of the afferent response to sinusoidal stretching of the triceps surae muscle was determined. Test measurements were made during tonic stretch of the ipsilateral PBSt, contralateral PBSt, contralateral triceps muscle or during extension of the intact contralateral hind limb. Control measurements were made with ipsi- and contralateral PBSt as well as contralateral triceps muscles relaxed and with contralateral hind limb in resting position. The occurrence and types of fusimotor effects were assessed by comparing test to control responses. The main finding of the present investigation was the great variability in type and size of the fusimotor effects evoked by different ipsi- and contralateral reflex stimuli. Both ipsi- and contralateral stimulations gave rise to predominantly dynamic, predominantly static or mixed static and dynamic fusimotor reflexes. In the same preparation, a given reflex stimulus often caused different reflex responses in different triceps surae primary spindle afferents. In the same afferent unit, different reflex stimuli usually produced fusimotor effects which differed from each other in type and/or size. In general, contralateral whole limb extension and stretch of contralateral PBSt muscles were more potent as reflex stimuli than stretch of the ipsilateral PBSt muscle. Stretch of the contralateral triceps surae muscle was, but for a few afferent units, ineffective as reflexogenic stimulus. It is concluded that the individualized receptive profiles of the primary muscle spindle afferents, which have been postulated in earlier investigations where the effects of different stimuli have been investigated on different cell populations, still seems to hold good when the stimuli are tested on the same units. The individuality of the receptive profiles of gamma-motoneurones is discussed in relation to different motor control hypotheses.     

Asymmetries and relationships between dynamic loading,muscle strength,and proprioceptive acuity at the knees in symptomatic unilateral hip osteoarthritis

Introduction

High joint loading, knee muscle weakness, and poor proprioceptive acuity are important factors that have been linked to knee osteoarthritis (OA). We previously reported that those with unilateral hip OA and bilateral asymptomatic knees are more predisposed to develop progressive OA in the contralateral knee relative to the ipsilateral knee. In the present study, we evaluate asymmetries in muscle strength and proprioception between the limbs and also evaluate relationships between these factors and joint loading that may be associated with the asymmetric evolution of OA in this group.

Methods

Sixty-two participants with symptomatic unilateral hip OA and asymptomatic knees were evaluated for muscle strength, joint position sense and dynamic joint loads at the knees. Muscle strength and proprioception were compared between limbs and correlations between these factors and dynamic joint loading were evaluated. Subgroup analyses were also performed in only those participants that fulfilled criteria for severe hip OA.

Results

Quadriceps muscle strength was 15% greater, and in the severe subgroup, proprioceptive acuity was 25% worse at the contralateral compared to ipsilateral knee of participants with unilateral hip OA (P <0.05). In addition, at the affected limb, there was an association between decreased proprioceptive acuity and higher knee loading (Spearman’s rho = 0.377, P = 0.007) and between decreased proprioceptive acuity and decreased muscle strength (Spearman’s rho = −0.328, P = 0.016).

Conclusions

This study demonstrated asymmetries in muscle strength and proprioception between the limbs in a unilateral hip OA population. Early alterations in these factors suggest their possible role in the future development of OA at the contralateral ‘OA-predisposed knee’ in this group. Furthermore, the significant association observed between proprioception, loading, and muscle strength at the affected hip limb suggests that these factors may be interrelated.     

Ipsilateral median somatosensory evoked potentials recorded from human somatosensory cortex

Somatosensory evoked potentials (SEP) to ipsilateral and contralateral median nerve stimulations were recorded from subdural electrode grids over the perirolandic areas in 41 patients with medically refractory focal epilepsies who underwent evaluation for epilepsy surgery. All patients showed clearly defined, high-amplitude contralateral median SEPs. In addition, four patients showed ipsilateral SEPs. Compared with the contralateral SEPs, ipsilateral SEPs were very localized, had a different spatial distribution, were of considerably lower amplitude, had a longer latency (1.2–17.8 ms), did not show an initial negativity, and were markedly attenuated during sleep. Stimulation of the subdural electrodes overlying the sensory hand area was associated with contralateral hand paresthesias, but no ipsilateral hand paresthesias occurred. It was concluded that subdurally recorded cortical SEPs to ipsilateral stimulation of the median nerve (M) reflect unconscious sensory input from the hand possibly serving fast bimanual hand control. The anatomical pathway of these ipsilateral short-latency MSEPs is not yet known. Transcallosal transmission seems unlikely because of the short delay between the ipsilateral and contralateral responses in selected cases. The infrequent occurrence of ipsilateral subdurally recorded SEPs and their low amplitude and limited distribution suggest that they contribute very little to the short-latency ipsilateral median SEPs recorded on the scalp.     

Bilateral convergence of pulmonary stretch receptor inputs on I beta-neurons in the cat

Extracellular recordings were made from inspiratory beta- (I beta) neurons in the nucleus of the tractus solitarius in decerebrate cats. A reversible direct current block of myelinated fibers in the ipsilateral vagus nerve was used to evaluate the input from pulmonary stretch receptor afferents (PSR) of the contralateral vagus to individual I beta-neurons. This block served to remove all ipsilateral (which includes all monosynaptic) inputs from PSR to I beta-cells. The effect of withholding inflation on the firing rate and the time of onset of firing of I beta-neurons was determined before, during and after application of the direct current block. There was considerable variation in the strengths of the inputs from the ipsilateral and contralateral nerves; some cells received PSR inputs from only the ipsilateral vagus, but the majority were excited with varying magnitude from both vagi. Several neurons had powerful excitatory inputs from PSR of the contralateral vagus, with the ipsilateral (monosynaptic) contribution being of minor importance.     

Abducens nerve responses of the frog during horizontal linear acceleration: data and model

Abducens nerve responses of frogs were evoked by sinusoidal oscillations on a horizontal linear sled. The depth of modulation of these responses and their phases depended on the orientation of the head with respect to the direction of linear acceleration. Longitudinal acceleration evoked abducens responses that consisted of two discharge maxima per stimulus cycle. At consecutively more oblique head orientations, one of these two discharge maxima increased and the other decreased. Transver se accelerations evoked abducens responses that consisted of only one discharge maximum per stimulus cycle. Removal of the labyrinthine organs on one side abolished these responses in the contralateral abducens nerve but did not affect the responses in the ipsilateral abducens nerve. The latter result indicates that the responses in each abducens nerve originate from hair cells on the contralateral utricle. The experimentally determined modulation and phase values and their dependence on the orientation ang le of the acceleration vector were used to characterize a functional cluster of hair cells located medially with respect to the striola in a fanlike sector on the utricle (‘lateral rectus fan’). Parameters of this fan were used to develop a model that satisfactorily simulates the recorded abducens responses. This model predicts a majority of afferents with excitatory and a few afferents with inhibitory contributions to the abducens nerve responses. The phasic response components of about 90% of these afferents are larger than their tonic response components. Received: 12 July 1993/Accepted in revised form: 11 October 1993     

Near-Infrared Transillumination Back Scattering Sounding—New Method to Assess Brain Microcirculation in Patients with Chronic Carotid Artery Stenosis

Purpose

The purpose of the study was to assess the responses of pial artery pulsation (cc-TQ) and subarachnoid width (sas-TQ) to acetazolamide challenge in patients with chronic carotid artery stenosis and relate these responses to changes in peak systolic velocity (PSV), cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time to peak response (TTP).

Methods

Fifteen patients with carotid artery stenosis ≥90% on the ipsilateral side and <50% on the contralateral side were enrolled into the study. PSV was assessed using colour-coded duplex sonography, CBF, CBV, MTT and TTP with perfusion computed tomography, cc-TQ and sas-TQ with near-infrared transillumination/backscattering sounding (NIR-T/BSS).

Results

Based on the ipsilateral/contralateral cc-TQ ratio after acetazolamide challenge two groups of patients were distinguished: the first group with a ratio ≥1 and the second with a ratio <1. In the second group increases in CBF and CBV after the acetazolamide test were significantly higher in both hemispheres (ipsilateral: +33.0%±8.1% vs. +15.3%±4.4% and +26.3%±6.6% vs. +14.3%±5.1%; contralateral: +26.8%±7.0% vs. +17.6%±5.6% and +20.0%±7.3% vs. +10.0%±3.7%, respectively), cc-TQ was significantly higher only on the ipsilateral side (+37.3%±9.3% vs. +26.6%±8.6%) and the decrease in sas-TQ was less pronounced on the ipsilateral side (−0.7%±1.5% vs. −10.2%±1.5%), in comparison with the first group. The changes in sas-TQ following the acetazolamide test were consistent with the changes in TTP.

Conclusions

The ipsilateral/contralateral cc-TQ ratio following acetazolamide challenge may be used to distinguish patient groups characterized by different haemodynamic parameters. Further research on a larger group of patients is warranted.     

Information processing in a cricket ganglion: The response of giant fibres to sound pulses

The response of giant fibres in the ventral nerve cord to stimulation of cercal afferents with pulses of sound was studied in the domestic cricket, Acheta domesticus. Pulses at 450 Hz gave the highest frequency response in several classes of units, and were therefore used as stimuli in subsequent experiments. In intact animals the response of the giant fibres to bilateral cercal stimulation showed a characteristic high frequency ‘on’ response followed by steady firing of some units for the duration of the sound pulse. The end of each pulse was followed by a short period of inhibition of the tonic units.Cercal amputation and other experiments showed that input from cercal afferents excites both large and small ipsilateral giants, and excites small and inhibits large contralateral giants. Descending input from higher neural centres in intact animals tends to reduce the responses to the stimuli. It is suggested that a function of the contralateral excitatory and inhibitory effects is to sharpen the ‘on’ response of the giant fibres to sound stimuli in intact animals.     

Binocular depth perception mechanisms in tongue-projecting salamanders

Tongue-projecting salamanders (Bolitoglossini) combine extreme speed and high precision in prey capture. They possess all requirements for stereoscopic depth perception: frontally oriented eyes, a substantial amount of direct ipsilateral projection in addition to the contralateral one, and binocularly driven neurons. Extracellular recordings were made from retinal afferents in the tectum as well as from the somata of tectal neurons. RF-sizes of afferents and tectal neurons were determined, and the response properties of tectal neurons were tested under monocular and binocular conditions with stimuli of different size and velocity. While RF-sizes and response properties of binocular neurons during binocular and contralateral stimulation were similar, ipsilaterally stimulated neurons exhibited much smaller RFs, lower spike rates and different size preferences.Furthermore, the contralateral retinotectal projection from one eye and the ipsilateral from the other are in register. While retinal afferents are distributed linearly over the tectal surface, most tectal neurons are activated by a retinal area corresponding to the frontal visual field; this results in a magnification of this region. The two monocular receptive fields of binocular neurons exhibit zero disparities (horopter) at distances that coincide with the maximum reach of the tongue. We hypothesize that bolitoglossine salamanders (as well as amphibians in general) make use of two kinds of disparities: (1) between the maps in the left and right tectal hemisphere, coding for the lateral eccentricity of an object, and (2) between the ipsilateral and contralateral retinotectal map, coding for the distance. The presence of substantial direct ipsilateral afferents in bolitoglossine salamanders appears to be the basis for a fast computation of object distance, which is characteristic of these animals.Abbreviations Ax/Ay coordinates of a recorded afference - Nx/Ny coordinates of a recorded neuron - RF receptive field - RFc contralateral receptive field - RFi ipsilateral receptive field - RFx/RFy coordinates of a receptive field center - RGC retinal ganglion cell     

Ghrelin selectively reduces mechanosensitivity of upper gastrointestinal vagal afferents

Ghrelin is a peptide released from gastric endocrine cells that has an orexigenic effect via a vagal pathway. Here we determine the effect of ghrelin on mechanosensitivity of upper-intestinal vagal afferent fibers in ferret and mouse. The responses of gastroesophageal vagal afferents to graded mechanical stimulation were determined in vitro before and during application of ghrelin to their peripheral endings. Three types of vagal afferent were tested: tension receptors responding to circumferential tension, mucosal receptors responding only to mucosal stroking, and tension/mucosal (TM) receptors in ferret esophagus that responded to both stimuli. In the mouse, ghrelin did not significantly affect the response of mucosal receptors to mucosal stroking with calibrated von Frey hairs. However, it significantly reduced responses of tension receptors to circumferential tension (P < 0.005; two-way ANOVA) by up to 40%. This inhibition was reversed by the ghrelin receptor antagonist [d-Lys-3]-growth hormone-releasing peptide (GHRP)-6. In the ferret, ghrelin significantly reduced the response of mucosal and TM receptors to mucosal stroking with calibrated von Frey hairs. Surprisingly, ghrelin did not significantly alter the response to circumferential tension in either tension or TM receptors. RT-PCR analysis indicated that both ghrelin and its receptor are expressed in vagal afferent cell bodies in mouse nodose ganglia. In conclusion, ghrelin selectively inhibits subpopulations of mechanically sensitive gastroesophageal vagal afferents; there is also potential for ghrelin release from vagal afferents. However, the subpopulation of afferents inhibited differs between species. These data have broad implications for ghrelin's role in food intake regulation and reflex control of gastrointestinal function.     

Modulation of immune responses following antigen administration by mucosal route

Most microbial infections are either restricted to the mucosal membranes or the etiologic agents needed to transit the mucosa. Thus, it is desirable to stimulate a mucosal response following vaccination, to block both infection and disease development. Attenuated vaccine carriers mimic natural infections, triggering also mucosal responses. Similar results can be achieved by administering antigens with appropriate adjuvants. However, the delivery of antigens per se is not sufficient to engender a protective response. A successful immunization requires the elicitation of an appropriate type of immune response (e.g. antibodies vs. cell-mediated immunity, Th1 vs. Th2 helper pattern). Therefore, a successful vaccination strategy demands the choice of adequate antigens, and their appropriate delivery and/or formulation to promote the required quality of immune response. Different strategies to optimize the immune responses elicited following vaccine administration by the mucosal route are discussed.     

Restoration of contralateral representation in the mouse somatosensory cortex after crossing nerve transfer

Avulsion of spinal nerve roots in the brachial plexus (BP) can be repaired by crossing nerve transfer via a nerve graft to connect injured nerve ends to the BP contralateral to the lesioned side. Sensory recovery in these patients suggests that the contralateral primary somatosensory cortex (S1) is activated by afferent inputs that bypassed to the contralateral BP. To confirm this hypothesis, the present study visualized cortical activity after crossing nerve transfer in mice through the use of transcranial flavoprotein fluorescence imaging. In naïve mice, vibratory stimuli applied to the forepaw elicited localized fluorescence responses in the S1 contralateral to the stimulated side, with almost no activity in the ipsilateral S1. Four weeks after crossing nerve transfer, forepaw stimulation in the injured and repaired side resulted in cortical responses only in the S1 ipsilateral to the stimulated side. At eight weeks after crossing nerve transfer, forepaw stimulation resulted in S1 cortical responses of both hemispheres. These cortical responses were abolished by cutting the nerve graft used for repair. Exposure of the ipsilateral S1 to blue laser light suppressed cortical responses in the ipsilateral S1, as well as in the contralateral S1, suggesting that ipsilateral responses propagated to the contralateral S1 via cortico-cortical pathways. Direct high-frequency stimulation of the ipsilateral S1 in combination with forepaw stimulation acutely induced S1 bilateral cortical representation of the forepaw area in naïve mice. Cortical responses in the contralateral S1 after crossing nerve transfer were reduced in cortex-restricted heterotypic GluN1 (NMDAR1) knockout mice. Functional bilateral cortical representation was not clearly observed in genetically manipulated mice with impaired cortico-cortical pathways between S1 of both hemispheres. Taken together, these findings strongly suggest that activity-dependent potentiation of cortico-cortical pathways has a critical role for sensory recovery in patients after crossing nerve transfer.     

Development of cortical somatosensory evoked potentials in rats.

The development of the contra- and ipsilateral cortical potential evoked by electrical sciatic nerve stimulation was studied in 77 male albino rats aged 5 to 45 days. A contralateral response was already recorded, as double negativity, in the youngest animals, while an ipsilateral evoked potential was not reliably present until the 10th day. At this time, however, both responses started with an inconstant positive wave and their shape was practically the same. During subsequent development the responses differed only in respect to their dominant component: in the contralateral response, the N1 wave had the highest amplitude for most of the time, while in the ipsilateral response the delayed N2 wave was the largest component. The latent periods of contralateral responses were somewhat shorter than those of ipsilateral evoked potentials. During development we noticed a phase of abrupt shortening of the latent period, which took place before the 15th day in the contralateral response and before the 20th day in the ipsilateral response. We also found a difference in the fatigability of the responses, which was greater in immature rats than in adult animals; in the ipsilateral evoked potential it approached adult values more slowly. The development of the ipsilateral response is thus delayed compared with the development of the contralateral response.     

Selective ablation of spinal afferent neurons containing CGRP attenuates gastric hyperemic response to acid.

The gastric mucosa, in particular submucosal blood vessels, are innervated by afferent neurons containing neuropeptides such as calcitonin gene-related peptide. Stimulation of sensory neurons innervating the gastric mucosa increases submucosal blood flow. Since sensory neurons supplying the stomach are of dual origin from nodose and dorsal root ganglia, we examined the effect of selective ablation of either the vagal or spinal sensory innervation to the upper gastrointestinal tract on the increase in gastric mucosal blood flow in response to acid back diffusion into the gastric mucosa. Perineural application of capsaicin to the celiac/superior mesenteric ganglia, but not to the vagus nerves, significantly inhibited by 53% the hyperemic response to acid back diffusion. Tissue levels of immunoreactive calcitonin gene-related peptide in the gastric corpus were significantly reduced (by 73%) by periceliac capsaicin treatment, but unaffected by perivagal capsaicin treatment. These data suggest that spinal capsaicin-sensitive afferents containing calcitonin gene-related peptide immunoreactivity are involved in mediating increases in gastric mucosal blood flow. This increase in gastric mucosal blood flow mediated by sensory neurons may act as a protective mechanism against mucosal injury, similar to responses seen in other tissues such as skin.     

Stimulation of vagal C-fibers alters timing and distribution of respiratory motor output in cats

Pulmonary vascular congestion or pulmonary embolism in humans produces shallow tachypnea, and indirect experimental evidence suggests that this characteristic breathing pattern may result from activation of vagal unmyelinated afferents from the lung. We have investigated, in decerebrate cats, reflex changes in breathing pattern and in the activation of the diaphragm, posterior cricoarytenoid, and thyroarytenoid muscles caused by activating C-fiber afferents in the vagus nerve. The right vagus nerve was sectioned distal to the origin of the recurrent laryngeal nerve, eliminating vagal afferent traffic although preserving motor innervation of the larynx on that side. The left cervical vagus was stimulated electrically, and efferent activation of the laryngeal muscles was avoided by cutting the left recurrent laryngeal nerve. Transmission to the brain of vagal afferent traffic resulting from this stimulation was controlled by graded cold block of the nerve cranial to the site of application of the stimulus. Activation of C-fibers, when A-fibers were blocked, significantly decreased respiratory period and amplitude of diaphragm inspiratory burst. In addition, this selective activation of vagal C-fibers augmented postinspiratory activity of the diaphragm and recruited phasic expiratory bursts in the thyroarytenoid. We conclude that, in unanesthetized decerebrate cats, afferent traffic of vagal C-fibers initiates a pontomedullary reflex that increases respiratory frequency, decreases tidal volume, and augments braking of expiratory airflow.     

Neurons of the ipsilateral and contralateral sensorimotor cortices in the cat: Their responses related to a conditioned reflex movement by one extremity

The activity of sensorimotor cortex neurons related to the performance of conditioned reflex movements by one extremity, which were evoked by the application of distant stimuli, was recorded in chronic experiments on cats. In the course of an experiment, the reflex performance was transferred from one extremity to the another, and, thus, the neuronal responses were studied in two situations: in the ipsilateral or in the contralateral position of a neuron with respect to the operating extremity. According to the pattern of their responses to the conditioning stimulus (CS), the neurons were classified into three groups. The first group consisted of neurons with bilateral type of responses, generating similar responses in both positions. The cells responding to the CS only in the ipsilateral situation formed the second group. The third group consisted of neurons with reciprocal responses, in the two above positions. The results obtained in our study illustrate basic regularities in the functioning of ipsilateral and contralateral hemispheres within the behavioral model used, and show that both hemispheres actively participate in the course of a preparation for the unilateral conditioned movement performance.Neirofiziologiya/Neurophysiology, Vol. 26, No. 5, pp. 334–346, September–October, 1994.     

Cosensitivity of vagal mucosal afferents to histamine and 5-HT in the rat jejunum

A complex sensitivity of afferent nerves in the mesentery of the rat jejunum to systemic administration of histamine has recently been demonstrated. In the present study, we aimed to characterize subpopulations of mesenteric afferents that mediate this afferent nerve response. Multiunit afferent discharge was recorded from mesenteric nerves supplying the proximal jejunum in anesthetized rats. The majority of mesenteric bundles (84%) exhibited biphasic responses to histamine (8 micromol/kg), and these bundles also responded to 2-methyl-5-HT (2m5HT). In contrast, monophasic responses lacked a short-latency component, and these bundles failed to respond to 2m5HT. Single-unit analysis revealed a population of afferents that possessed cosensitivity for 2m5HT and histamine. This population of afferents was absent in chronically vagotomized animals, whereas mucosal anesthesia with luminal lidocaine reversibly converted the biphasic profile to a monophasic one. Ondansetron (500 microg/kg) blocked the response to 2m5HT with no effect on the profile of the histamine response, whereas pyrilamine (5 mg/kg) blocked the histamine response without affecting the response to 2m5HT. We conclude that histamine-sensitive afferents exist in the rat proximal jejunum that also respond to 5-HT via the 5-HT3 receptor. These fibers appear to be vagal afferents originating in the intestinal mucosa and may be involved in the organization of mast cell-mediated responses.