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Sensory Pathway (sensory + pathway)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Peripheral sensitization in migraine,role for P2X purinergic receptors in the dura,vascular sensory pathway

DRUG DEVELOPMENT RESEARCH, Issue 6 2007
Ernest A. Jennings
Abstract Peripheral sensitization is still considered a prime contributor underlying the mechanisms of migraine. Trigeminal primary afferent neurons are the first neurons in the dural nociceptive pathway, and activation results in conscious perception of pain. Peripheral sensitization can lower the activation threshold of primary afferent neurons, rendering them more excitable, allowing for increases in release of neurotransmitter from both central and peripheral terminals. Increase in neurotransmitter release from central terminals contributes to excitation of second-order neurons, while the release of peptides from peripheral terminals has been implicated in neurogenic inflammation. Adenosine 5,-triphosphate (ATP) causes pain in human studies, and depolarize sensory neurons. There is evidence of the action of ATP at many levels in the dura,vascular sensory pathway. Animal studies have shown that some P2X receptors are located in neurons innervating the dura, including the P2X3 receptor, which is most often shown to be involved in nociceptive pathways. In this article, we briefly review peripheral sensitization in relation to migraine and provide emphasis for P2X receptor involvement where it is available. Drug Dev Res 68:321,328, 2007. © 2007 Wiley-Liss, Inc. [source]

CLINICAL, MRI, AND SKIN BIOPSY FINDINGS IN SENSORY GANGLIONOPATHIES

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2000
A. Sghirlanzoni
Unlike peripheral motor disorders, sensory disturbances are rarely diagnosed by the probable site of pathology. This approach is useful in the differential diagnosis between chronic sensory axonal neuropathies and ganglionopathies, in which routine clinical and neurophysiological evaluation alone often do not provide definite clues. Methods: Thirty patients with peripheral sensory disturbances were investigated. MRI was performed at cervical level in all cases. Four patients also underwent thoracic and lumbar MRI. Seventeen patients underwent skin biopsy at the proximal thigh and the distal leg. In 4 of them, further skin biopsies were taken at C5 dermatome and at the hand. Density of intra-epidermal nerve fibers (IENF) was quantified. Results: In 22 patients, sensory ganglionopathy was suspected. Disease was idiopathic in 7 cases; paraneoplastic in 3 cases; and associated with Sjögren, AIDS, autoimmune chronic hepatitis, and cisplatin neurotoxicity in 4 cases. One patient had a hereditary sensory autonomic neuropathy. Four patients had vitamin E deficiency and 3 patients a spinocerebellar syndrome. In 8 patients, sensory axonal neuropathy related to diabetes, alcoholism, and AIDS on antiretroviral treatment, and monoclonal gammopathy of undetermined significance was diagnosed. MRI findings: All ganglionopathy patients showed posterior columns hyperintensity on T2-weighted MRI. Conversely, MRI was negative in all axonal sensory neuropathy patients. Skin biopsy findings: In neuropathies, IENF density was significantly lower at the distal leg than at the proximal thigh, while ganglionopathies did not show any change with respect to the rostral:caudal orientation. A similar pattern of epidermal denervation was observed in the arm. Discussion: The degeneration of both central and peripheral sensory pathway in a fashion that is not length-dependent localizes the disease to T-shaped sensory neurons Early ataxia and cutaneous sensory symptoms involving the proximal regions of the body reflect this pattern of denervation and should prompt the diagnosis of ganglionopathy. This can be confirmed by T2-weighted hyperintensity in the posterior columns and a distinct pattern of IENF loss. [source]

Peripheral synapses and giant neurons in whip spiders

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2002
Rainer Foelix
Among invertebrates the synapses between neurons are generally restricted to ganglia, i.e., to the central nervous system (CNS). As an exception, synapses occur in the sensory nerves of arachnid legs, indicating that some nervous integration is already taking place far out in the periphery. In the antenniform legs of whip spiders (Amblypygi), a very special synaptic circuit is present. These highly modified legs contain several large interneurons (giant neurons) that receive mechanosensory input from 700,1,500 tarsal bristles. Some of the sensory cell axons contact a giant neuron at its short, branched dendrite, a few at the soma, but most synapse onto the long giant axon. The fine structure of these synapses resembles that of typical chemical synapses in other arthropods. Although thousands of sensory fibers converge on a single giant neuron, there is no reduction in the actual number of sensory fibers, because these afferent fibers continue their course to the CNS after having made several en passant synapses onto the giant neuron. Touching a single tarsal bristle is sufficient to elicit action potentials in a giant neuron. Owing to the large diameter of the giant axon (10,20 ,m), the action potentials reach the CNS within 55 ms, at conduction velocities of up to 7 m/s. However, mechanical stimulation of the tarsal bristles does not elicit a fast escape response, in contrast to giant fiber systems in earthworms, certain insects, and crayfishes. A quick escape is observed in whip spiders, but only after stimulation of the filiform hairs (trichobothria) on the regular walking legs. Although the giant fiber system in the antenniform legs undoubtedly provides a fast sensory pathway, its biological significance is not clearly understood at the moment. Microsc. Res. Tech. 58:272,282, 2002. © 2002 Wiley-Liss, Inc. [source]

Oral mucosal versus cutaneous sensory testing: a review of the literature

JOURNAL OF ORAL REHABILITATION, Issue 10 2002
R. Jacobs
summary, The innervation of skin and oral mucosa plays a major physiological role in exteroception. It also has a clinical interest as illustrated by sensory changes after neurosurgical procedures. These sensory changes often rely only on the patients' subjective reports, although objective assessments are possible. This review compares the neurophysiological features of the trigeminal sensory pathways with those of cutaneous sensory innervation. In this review, three receptor groups will be discussed: mechanoreceptors, thermoreceptors and nociceptors. Differences between receptors in the glabrous skin, the hairy skin and the oral mucosa will be highlighted. Sensory testing devices have been developed to quantify psychophysiological parameters such as the threshold level for receptor activation upon mechanical stimulation, but such devices have been merely developed to determine the threshold of skin receptors (tactile, thermal). Later on, some have been adapted to suit the particularities of the oral environment. This review attempts to compare the available literature on test devices for oral versus cutaneous tactile function. It summarizes what is common or rather particular to the devices used to study either cutaneous or oral receptors. [source]

Activation of peripheral 5-HT4 receptors attenuates colonic sensitivity to intraluminal distension

NEUROGASTROENTEROLOGY & MOTILITY, Issue 1 2006
B. Greenwood-van Meerveld
Abstract, Tegaserod is a 5-HT4 receptor partial agonist approved for the treatment of irritable bowel syndrome in women with constipation and in both men and women with chronic constipation. The efficacy of tegaserod is based on the importance of 5-HT4 receptors regulating intestinal peristalsis and secretion, and possibly visceral sensory pathways. Our aim was to investigate the effect of tegaserod on colorectal sensitivity using models of normal and exaggerated responsiveness to colorectal distension (CRD). The visceromotor responses (VMR) to CRD at graded pressures (0,60 mmHg) were measured by the number of reflex abdominal contractions. Acute colorectal hypersensitivity was induced by intracolonic infusion of dilute acetic acid. Chronic hypersensitivity was observed in rats following spontaneous resolution of trinitrobenzenesulfonic acid-induced colitis. Rats with normosensitive colons served as controls. Tegaserod (0.1,10 mg kg,1) caused dose-dependent reduction of the VMR to CRD in control rats and in those with colonic hypersensitivity. 5-HT4 antagonists reversed the effects of tegaserod in rats with normosensitive colons, and partially inhibited effects in rats with colonic hypersensitivity. Central administration of tegaserod had no inhibitory effect. These results support the assumption that colonic hypersensitivity could be normalized by tegaserod acting, at least in part, through peripheral 5-HT4 receptors. [source]

ATD perimetry in glaucoma and ocular hypertensive patients.

ACTA OPHTHALMOLOGICA, Issue 2007
A preliminar study
Purpose: The new ATD perimetry assesses contrast sentivity thresholds for the three afferent sensory pathways of the visual system. Our aim is to compare contrast sensitivity to stimuli with different spatio-temporal frequencies in glaucomatous (G) and ocular hypertensive (OHT) subjects. Methods: Twenty three G and OHT subjects were selected from the ophthalmic clinic, all subjects signed an informed consent. Inclusion criteria were diagnosis of G or OHT, normal Farnsworth-Munsell color test, ametropia less than 6 D, visual acuity over 20/30, absence of previous ocular surgery and experience in perimetry. Twenty locations and the fovea were evaluated in a 60º x 40º fovea-centered field. Eight gabor stimuli were used: 0.5cpd-12Hz, 0.5cpd-24Hz, 4cpd-2Hz and 4cpd 12Hz, modulated along the achromatic (A) direction, 0.5cpd-12Hz and 4cpd-2Hz along the red/green (T) and blue/yellow (D) directions. Statistical analysis included ANOVA and Schéffé tests. Results: Mean thresholds for G and OHT were respectively, 0.4872 ± 0.5323 and 0.1077 ± 0.1922, for A 0.5cpd-12Hz; 0.7296 ± 0.5925 and 0.2280 ± 0.2246 for stimulus A 0.5cpd-24Hz; 1.4444 ± 0.5244 and 1,2671 ± 0.6138 for A 4cpd-2Hz; and 0.7751 ± 0.1937 and 0.6851 ± 0.2379 for D 0.5cpd-12Hz. Significant statistical differences (p<0.05) were found between G and OHT groups only with these stimuli. Conclusions: These preliminary results show that certain stimuli may differentiate between G and OHT subjects. A larger population sample, including glaucoma suspects, is currently under study. [source]