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At least 19 recordsLinked to original sources
PubMed1978

Characterization and ionic basis of GABA-induced depolarizations recorded in vitro from cat primary afferent neurones.

1. Responses of single cells in the isolated cat spinal ganglion to GABA applied by superfusion or by iontophoresis were recorded using intracellular micro-electrodes. 2. Of the twelve structurally related compounds investigated, GABA was the most effective in its ability to produce a depolarization of the cell membrane. 3. Studies determining concentration-response relationships indicate that two to three molecules of GABA are required to combine with the GABA receptor for activation. 4. Bicuculline and picrotoxin, each act in a non-competitive manner to antagonize the GABA-induced membrane current. 5. The equilibrium potential for iontophoretically induced GABA depolarizations (EGABA) was found to be -23.5 plus or minys 6.1 mV. EGABA was independent upon [cl-]o, but independent of [Na+]o, [K+], or [Ca2+]o. 6. Intracellular injection of twenty antions (Br-, I-, NO2-, NO3-, ClO4-, SCN-, Bf4-, HS-, OCN-, ClO3-, BrO3-, F-, HCO2-, HSO3-, HCO3-, CH3CO2-, SO42-, C6H5O73-) indicated that the activated GABA receptor membrane was permeable to those anions whose hydrated diameter is no larger than that of ClO-3. 7. Restoration of the GABA depolarization to its control level after augmentation by Cl- injection had a mean time constant of 27.8 plus or minus 2.6 min. Picrotoxin did not alter this value. 8. When foreign anions were exchanged for Cl- in the perfusion solution, the ten anaions smaller or equal to ClO3-, decreased the GABA depolarization by 50-90% and increased its time course 1.5-2.0 x control. The only exception having a small radius was Br- which augmented the amplitude 10-30%. 9. The ten anions larger than ClO3- produced a biphasic effect, i.e. an initial augmentation followed by a marked (up to 100%) depression of the response. Experiments with CH3COO-, CH3SO4-, or HOCH2CH2SO3-, indicated that this depression was non-competitive.

Aminobutyrates↗
PubMed1978

Segmental reflexes mediated by joint afferent neurons in cat knee.

1. Reflex effects mediated by knee joint afferent neurons were tested using the electrically evoked monosynaptic reflex in motoneurons innervating muscles which act about the knee. 2. Joint afferents were excited using small extension movements of the knee, stimuli which have been shown to be effective in activating a large fraction of the myelinated fibers in joint nerves. Because of the variability of reflex responses observed by others under similar experimental conditions, experimental control and data collection were done automatically under computer control. Large numbers of trials were presented in random sequence, and the resulting data were sorted and averaged. 3. Positive feedback was observed in both knee extensor (vasti) and knee flexor (posterior biceps-semitendinosus (PB-ST)) motoneuron populations. Vasti motoneurons were excited, and PB-ST motoneurons were inhibited by knee extensions when the posterior articular nerve (PAN) was intact; these effects were lost or substantially reduced when the PAN was cut. 4. Using knee extension stimuli, no reliable reflex effects were observed which could be attributed to afferents in medial articular nerve.

Animals↗
PubMed1979

Spinal termination of functionally identified primary afferent neurons with slowly conducting myelinated fibers.

Single primary afferent myelinated fibers from cutaneous receptors of cat and monkey were functionally identified by recording from the spinal cord with micropipettes filled with horseradish peroxidase (HRP). Relatively slowly conducting fibers (less than 40 m/sec) from high threshold mechanoreceptors (mechanical nociceptors) and two types of low threshold mechanoreceptor (D-hair and field) were selected for staining. Iontophoresis of the HRP and subsequent histochemical reaction stained the axons recorded from and their collaterals, including terminations, for several millimeters. The termination patterns in the two species proved essentially identical. Ipsilaterally, the mechanical nociceptor fibers terminated principally in the dorsal horn's marginal zone and in the ventral parts of the nucleus proprius (lamina V in the cat). Some of these nociceptors also had terminals in the midline just dorsal to the central canal, contralaterally in the marginal zone, and at the base of the opposite nucleus proprius. In contrast, the D-hair primary afferent axons terminated in the dorsal part of the nucleus proprius overlapping into the innermost portion of the substantia gelatinosa. The field receptor fibers terminated predominantly in the middle part of the nucleus proprius. These results suggest that there is a highly specialized central projection of primary afferent endings which is related to sensory function and not to fiber diameter. The marginal zone and most dorsal parts of the substantia gelatinosa receive direct projections from cutaneous nociceptors but do not have direct input from cutaneous receptors transmitting activity initiated by innocuous stimulation.

Animals↗
PubMed1978

The morphology of the spinal cord efferent and afferent neurons contributing to the ventral roots of the cat.

Horseradish peroxidase was applied to proximal ventral roots of the coccygeal and sacral spinal cord of cats. Subsequent histochemical reaction resulted in extensive staining of spinal cord neurons that had processes in the ventral roots. This procedure was used to study four issues concerning ventral root neurons. (1) Extensive transverse dendritic arborizations were revealed for large and small neurons presumed to be alpha and gamma motoneurons respectively. Dendrites from these neurons were found to project heavily into the ipsilateral white matter, both laterally and ventrally. Dendrites also projected extensively through the anterior commissure, attaining the contralateral grey and white matter. (2) Medially-located efferent neurons were found to contribute the contralateral dendrites as well as some dorsally-directed dendrites. Laterally-located neurons projected dendrites extensively into the lateral and ventral white matter. (3) Stained neurons were found in the intermediolateral cell column, and were presumed to be preganglionic efferent neurons. Some of these neurons projected dendrites into the marginal zone of the dorsal horn, while others sent dendrites medially toward the central canal. (4) Stained fibers, presumed to be primary afferents, were found to enter from the ventral roots and course to the dorsal horn. Most of these fibers were small in diameter and distributed boutons predominantly to the substantia gelatinosa. A few large ventral root afferent fibers were observed that distributed boutons mostly to the nucleus proprius.

Animals↗
PubMed1977

Response of primate joint afferent neurons to mechanical stimulation of knee joint.

1. One hundred thirty-eight knee joint afferents from posterior articular nerve (PAN), in primates, were recorded in dorsal root filaments. Responses of afferents were studied in relation to both passive manipulations of the knee and active contractions of quadriceps, semimembranosus, and gastrocnemius muscles. 2. When the knee was passively rotated, most neurons discharged only when extreme angular displacements were achieved. Response of neurons responding to passive extensions was linearly related to the torque applied to the knee. With maintained extensions, discharge in extension neurons adapted slowly. Some of the time constants of adaptation were similar to those for simultaneously recorded torque relaxation. 3. Contractions of quadriceps, semimembranosus, or gastrocnemius muscles could activate many neurons in the absence of changes in joint angle. For quadriceps-activated neurons, rather high torques (mean = 2,450 g with cm) were required. 4. The results support the hypothesis that joint afferents function as capsullar stretch receptors, responding to those mechanical events which result in loading of the capsule.

Adaptation, Physiological↗
PubMed1975

Demonstration of a pallido-nigral projection innervating dopaminergic neurons.

Afferents to the substantia nigra from the neostriatum and globus pallidus were studied in the rat by means of the autoradiographic tracing technique. 3H-leucine was injected stereotaxically into either the globus pallidus or neostriatum. Twenty-four hours later the axoplasmic transport of labelled proteins to the substantia nigra was studied by light and electron microscopic autoradiography. In animals used for electron microscopy, degeneration of dopaminergic cells in the substantia nigra was induced by intraventricular injection of 6-hydroxydopamine 72 hours before sacrifice. After neostriatal injections, light microscopic analysis revealed heavy labelling of the globus pallidus and entopeduncular nucleus, but only background labelling of the subthalamic nucleus. There was preferential labelling of the zone reticulata of the substantia nigra, with significantly less labelling of the zone compacta. After pallidal injections, light microscopic analysis showed very light labelling of those parts of the caudate-putamen in the vicinity of the injection site. There was intense labelling of the subthalamic nucleus and heavy labelling of the entopeduncular nucleus. The zona compacta of the substantia nigra was also heavily labelled. There was considerably less labelling of the zona reticulata. The electron microscopic analyses showed that after neostriatal injections, autoradiographic grains in the substantia nigra were located preferentially over boutons which terminated on normal dendritic processes. After pallidal injections, however, grains were preferentially located over boutons synapsing with degenerating dendritic processes. The degeneration produced in these dopaminergic processes by 6-hydroxydopamine was invariably of the dark type. Except for the different association with degenerating vs. non-degenerating dendrites, the subcellular distribution of autoradiographic grains in the substantia nigra was the same after injection into either the globus pallidue or caudate-putamen. Approximately 80 percent of the grains were over axons or boutons which invariably made symmetrical synaptic contacts. These observations demonstrate the existence of a pallido-nigral projection which terminates preferentially on dopaminergic cells in the pars compacta of the substantia nigra. They also confirm previous studies indicating that the strionigral projection terminates mainly in the pars reticulata. These terminations appear to be principally to non-dopaminergic cells.

Animals↗
PubMed1979

[Contribution of ultrastructural analysis to the knowledge of the neuromuscular relationships in the nodal and conduction tissue].

The ultrastructure of the atrio-ventricular junction in the rat heart fixed in situ was studied on serial fine sections. The relationships between the specialized tissue and the nervous system were studied after labelling adrenergic endings with 5-OH-dopamine. Among the various types of nerve endings a distinction may be made between: 1) adrenergic or cholinergic free endings; 2) large "cluster" endings of the cholinergic types, seen mainly in the equatorial regions of nodal cells; 3) small diameter cholinergic before the development of heart failure or significant card synaptic images; 4) afferent neurons, whose endings, rich in glycogen and mitochondria supply the conduction tissue fibres, getting into or through the muscle fibre. The intermembrane space is then 20 nm. The analogy between the images observed and the ultrastructural aspects of intrafusorial fibres in skeletal muscle is discussed.

Adrenergic Fibers↗
PubMed1975

[The role of afferent barosensory neurons in respiratory and bronchomotor control].

Ventilatory and bronchomotor responses to baroreceptor afferent stimulation were studied in anaesthetized rabbits breathing spontaneously. The stimuli used were either the increase in carotid sinus pressure or the electrical stimulation of the cut central end of the aortic nerve. Respiratory effects of aortic barodenervation were also studied. Normoxic, normocapnic steady state was verified by repeated measurement of PO2, PCO2 and pH in arterial blood. Stimulation of both aortic and carotid baroreceptors provoked an early decrease of tidal volume and total pulmonary resistances without change in respiratory frequency. Aortic nerve stimulation induced an important and slowly adapting ventilatory and bronchomotor effect, whereas changes in carotid sinus pressure produced slight variation in respiratory parameters. Aortic nerve section resulted in an early and prolonged increase of total pulmonary resistances. Surgical or chemical (atropine) vagotomy did not change the bronchodilation observed under stimulation of the carotid sinus; however this effect was suppressed by intravenous injection of propranolol. This observation shows the importance of the sympathetic outflow in the genesis of bronchomotor responses following baroreceptor stimulation. In conclusion the baroreceptor stimulation provokes simultaneous decrease of both ventilation and total pulmonary resistances; aortic nerves seemed to exert permanent control on bronchomotor tone.

Animals↗
PubMed1977

Neuronal and synaptic organization in the gravity receptor system of the statocyst of Octopus vulgaris.

The neuronal and synaptic organization of the sensory epithelium (macula) of the gravity receptor system of Octopus vulgaris was investigated by serial electron microscopic reconstruction. Three different types of afferent neurons, unipolar, bipolar, and multipolar, are described. Afferent synapses exist between the secondary sensory cells (hair cells) and the afferent neurons. Consequently, the neurons are first-order neurons. Two morphologically distinct types of afferent synapses could be identified: the most common type, present on every hair cell, has a finger-like postsynaptic process; the second type, which does not occur on every hair cell, has a flat or somewhat curved postsynaptic process. As a rule, the hair cells each form synapses with more than one afferent neuron. The neurons, in turn, form synapses with more than one hair cell. A complicated arrangement of efferent synapses was found at the level of both the hair cells and the neurons. The results are discussed with reference to their physiological consequences.

Animals↗