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Results for “NERVE ENDINGS”

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At least 19 recordsLinked to original sources
PubMed1990

Ultrastructural three-dimensional reconstruction of group III and group IV sensory nerve endings ("free nerve endings") in the knee joint capsule of the cat: evidence for multiple receptive sites.

The noncorpuscular endings ("free nerve endings") of thinly myelinated group III and nonmyelinated group IV afferent nerve fibers have been examined in the knee joint capsule of sympathectomized cats by transmission electron microscopy and three-dimensional reconstruction of series of semi- and ultrathin sections. The sensory ending is the most distal part of a group III or IV nerve fiber that consists only of the sensory axon and associated Schwann cells but lacks a myelin sheath and is not surrounded by perineurium. The sensory axon divides into several branches and forms a terminal tree. The branches run either as single fibers or within small Remak bundles in parallel to sensory axons of other endings; they spread along vessel walls and also extend into dense connective tissue. Each sensory axon consists of a series of spindle-shaped thick segments ("beads") connected by waist-like thin segments. Thus all axons of sensory endings have a string-of-beads appearance, which resembles that of efferent sympathetic nerve fibers. The beads of the sensory axon and the end bulb at its tip show the same ultrastructural features which are characteristic of receptive sites: an accumulation of mitochondria and glycogen particles and various vesicles in the axoplasm and "bare" areas of axolemma that are not covered by Schwann cell processes. Group III and group IV sensory endings differ in the length of their branches (up to 200 microM in group III vs. more than 300 microM in group IV), number of beads per 100 microM axon length (about seven vs. nine or ten), mean diameter of axons (0.9-1.5 microM vs. 0.3-0.6 microM), and the presence of a neurofilament core consisting of bundles of parallel microfilaments only in group III. In conclusion, we propose that the sensory part of noncorpuscular "free nerve endings" is formed by the entire terminal tree of group III or group IV nerve fibers and that the beads in the course of the sensory axon represent multiple receptive sites.

Animals↗
PubMed2001

The role of sensory nerve endings in nerve growth factor-induced airway hyperresponsiveness to histamine in guinea-pigs.

1. Nerve growth factor induces an airway hyperresponsiveness in vivo in guinea-pigs, as we have shown previously. Since antagonizing the neurokinin-1 (NK(1)) receptor can prevent this NGF-induced airway hyperresponsiveness and since sensory nerves release tachykinins, we investigated the role of sensory nerves in the NGF-induced airway hyperresponsiveness. 2. We used isolated tracheal rings from guinea-pigs to measure tracheal contractility. In these rings sensory nerve endings are present, but these endings lack any contact with their cell bodies. 3. In this in vitro system, NGF dose-dependently induced a tracheal hyperresponsiveness to histamine. The NK(1) receptor antagonist SR140333 could block the induction of tracheal hyperresponsiveness. 4. To further investigate the involvement of sensory nerve endings we used the cannabinoid receptor 1 (CB(1)) agonist R-methanandamide to inhibit excitatory events at the nerve terminal. The CB(1) receptor agonist was capable of blocking the tracheal hyperresponsiveness to NGF in the isolated system, as well as the airway hyperresponsiveness to NGF in vivo. 5. This indicates that NGF can induce an increase in airway responsiveness in the absence of sensory nerve cell bodies. NGF may act by increasing substance P release from sensory nerve endings, without upregulation of substance P in the neurons. Substance P in its turn is responsible for the induction of the NGF-induced airway hyperresponsiveness.

Airway Resistance↗
PubMed1989

Na+ channel accumulation on axolemma of afferent endings in nerve end neuromas in Apteronotus.

In mammals, cut sensory axons trapped in a nerve end neuroma have been shown to develop hyperexcitability, and to become a source of ectopic afferent discharge and abnormal sensation. We have explored cellular mechanisms underlying neuroma electrogenesis. First we confirmed that ectopic neuroma discharge develops in injured afferents in the electrosensory lateral line nerve of the weakly electric fish Apteronotus, as it does in mammals. Then, using previously characterized antibodies that specifically recognize Na+ channel proteins in this species, we obtained light and electron microscopic evidence of abnormally intense immunolabelling of axolemma at the injury site. Accumulation of excess Na+ channels in afferent endings in neuromas could account for their electrical hyperexcitability.

Animals↗
PubMed1998

[The distribution of nerve endings in the human cervical nerve roots].

OBJECTIVE: To find out the distribution of nerve endings in the dural sheath of cervical nerve roots and to study the mechanism of cervical radicular pain. METHOD: 2069 20 microm serial sections were made from 39 cervical root-dorsal root ganglion specimens obtained from 18 postmortems. By using optical microscope and Suzuki silver impregnation method and Klüver-Brrera method, we examined the morphology, quantity and distribution of the nerve ending in the nerve sheath of the root, dorsal root ganglion (DRG) and the spinal nerve of these sections. RESULT: There were several kinds of nerve endings such as free nerve endings in the nerve sheath of the root, the dorsal root ganglion, and the spinal nerve. Free nerve endings were distributed in the proximal and distal portions of DRG sheath more extensive than that in other parts of the dural root-sheaths. CONCLUSION: The free nerve endings in the dural root-sheaths especially those in the DRG sheath are thought to play an important role in cervical radicular pain.

Adolescent↗
PubMed1983

Scanning electron microscopy of the nerve endings of Corti's organ.

Scanning electron microscopy (SEM) study of the innervation of the organ of Corti has been carried out for many years. Various methods have been used in attempts to observe more details of the endings of nerve fibers on the sensory hair cells. In this study, a new method of microdissection of Corti's organ was done using a small piece of double-sided adhesive tape. This method is simple and facilitates observation of Corti's organ from the basal to the apical turns. Using it we found variations of the nerve endings and the Deiters' cells in each half turn beginning from the lower basal turn to the upper fourth turn. Nerve endings at the lower poles of outer hair cells are arranged in clusters, and are reduced in size and number as the upper turn is approached. On the contrary, the Deiters' cells are increased in size toward the upper turn, therefore nerve endings in the upper turn are often covered by Deiters' cells. Small nerve endings high on the side of the outer hair cell were also observed. Although there was clear evidence of ultrastructural change in the hair cells' cilia after administration of ototoxic drugs or after hyperstimulation by sound, there was no evidence of concomitant ultrastructural change in the nerve endings. Nerve endings appeared to be more resistant than the hair cells.

Acoustic Stimulation↗
PubMed1981

Biochemical approaches to the study of cytosolic calcium regulation in nerve endings.

The nerve ending cytosol is bounded by the plasma membrane, the mitochondrial inner membrane and the endoplasmic reticulum membrane, transport across each of which is capable, in theory, of regulating the cytosolic free Ca2+ concentration. By parallel monitoring of mitochondrial and plasma membrane potentials, ATP levels, Na+ gradients and intrasynaptosomal Ca2+ distribution in preparations of isolated synaptosomes, we conclude the following: (a) mitochondria in situ represent a major Ca2+ pool, regulating the upper steady-state limit of the cytosolic free Ca2+ concentration by sequestering Ca2+ reversibly; (b) this limit is responsive to the cytosolic Na+ concentration, but is below the concentration required for significant exocytosis; (c) plasma membrane Ca2+ transport can be resolved into a constant slow influx, a voltage-dependent and verapamil-sensitive influx and an ATP-dependent efflux, while Ca2+ efflux driven by the sodium electrochemical potential cannot be detected; (d) Ca2+ regulation by intrasynaptosomal endoplasmic reticulum appears to be of minor significance in the present preparation.

Animals↗
PubMed1981

Biochemistry and ultrastructure of serotonergic nerve endings in the lobster: serotonin and octopamine are contained in different nerve endings.

In this article we report that the distribution of serotonin in the lobster nervous system parallels the distribution of octopamine and that the same tissues that contain endogenous serotonin can synthesize it from tryptophan. Octopamine and serotonin are highly concentrated in a neurosecretory region of the second thoracic roots in association with a group of neurosecretory cells. The roots possess separate high-affinity uptake systems for both serotonin and tryptophan. Radioactive serotonin, accumulated in tissues during incubations with either tritiated serotonin or tritiated tryptophan, can be released, in a calcium-dependent manner, by depolarization with potassium. A detailed morphological examination of the second thoracic roots shows four distinct categories of nerve endings in the vicinity of the neurosecretory cells. Octopamine is synthesized in one of these types of endings and serotonin in another. The high-affinity uptake systems for serotonin and tryptophan are found only in association with the endings that make serotonin. These endings and all the biochemical parameters of serotonin metabolism in the roots are selectively destroyed by previous injection of animals with the neurotoxin 5,7-dihydroxytryptamine.

Animals↗