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Ablation of primary afferent terminals reduces nicotinic receptor expression and the nociceptive responses to nicotinic agonists in the spinal cord.
J Neurocytol. 2004 Sep; 33(5):543-56.JN

Abstract

A variety of studies indicate that spinal nicotinic acetylcholine receptors modulate the behavioral and autonomic responses elicited by afferent stimuli. To examine the location of and role played by particular subtypes of nicotinic receptors in mediating cardiovascular and nociceptive responses, we treated neonatal and adult rats with capsaicin to destroy C-fibers in primary afferent terminals. Reduction of C-fiber terminals was ascertained by the loss of isolectin B4, CGRP and vanilloid receptors as monitored by immunofluorescence. Receptor autoradiography shows a reduction in number of epibatidine binding sites following capsaicin treatment. The reduction is particularly marked in the dorsal horn and primarily affects the class of high affinity epibatidine binding sites thought to modulate nociceptive responses. Accompanying the loss of terminals and nicotinic binding sites were significant reductions in the expression of alpha 3, alpha 4, alpha 5, beta 2 and beta 4 nicotinic receptor subunits in the superficial layers of the spinal cord as determined by antibody staining and confocal microscopy. The loss of nicotinic receptors that follows capsaicin treatment results in attenuation of the nociceptive responses to both spinal cytisine and epibatidine. Capsaicin treatment also diminishes the capacity of cytisine to desensitize nicotinic receptors mediating nociception, but it shows little effect on intrathecal nicotinic agonist elicited pressor and heart rate responses. Hence, our data suggest that alpha 3, alpha 4, alpha 5, beta 2 and beta 4 subunits of nicotinic receptors are localized in the spinal cord on primary afferent terminals that mediate nociceptive input. A variety of convergent data based on functional studies and subunit expression suggest that alpha 3 and alpha 4, in combination with beta 2 and alpha 5 subunits, form the majority of functional nicotinic receptors on C-fiber primary afferent terminals. Conversely, spinal nicotinic receptors not located on C-fibers play a primary role in the spinal pathways evoking spinally coordinated autonomic cardiovascular responses.

Authors+Show Affiliations

Department of Pharmacology, University of California, San Diego, CA 92093-0636, USA. ikhan@ucsd.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15906161

Citation

Khan, Imran M., et al. "Ablation of Primary Afferent Terminals Reduces Nicotinic Receptor Expression and the Nociceptive Responses to Nicotinic Agonists in the Spinal Cord." Journal of Neurocytology, vol. 33, no. 5, 2004, pp. 543-56.
Khan IM, Wennerholm M, Singletary E, et al. Ablation of primary afferent terminals reduces nicotinic receptor expression and the nociceptive responses to nicotinic agonists in the spinal cord. J Neurocytol. 2004;33(5):543-56.
Khan, I. M., Wennerholm, M., Singletary, E., Polston, K., Zhang, L., Deerinck, T., Yaksh, T. L., & Taylor, P. (2004). Ablation of primary afferent terminals reduces nicotinic receptor expression and the nociceptive responses to nicotinic agonists in the spinal cord. Journal of Neurocytology, 33(5), 543-56.
Khan IM, et al. Ablation of Primary Afferent Terminals Reduces Nicotinic Receptor Expression and the Nociceptive Responses to Nicotinic Agonists in the Spinal Cord. J Neurocytol. 2004;33(5):543-56. PubMed PMID: 15906161.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Ablation of primary afferent terminals reduces nicotinic receptor expression and the nociceptive responses to nicotinic agonists in the spinal cord. AU - Khan,Imran M, AU - Wennerholm,Michelle, AU - Singletary,Erin, AU - Polston,Kimberley, AU - Zhang,Limin, AU - Deerinck,Tom, AU - Yaksh,Tony L, AU - Taylor,Palmer, PY - 2004/06/22/received PY - 2005/02/02/accepted PY - 2005/01/31/revised PY - 2005/5/21/pubmed PY - 2005/9/1/medline PY - 2005/5/21/entrez SP - 543 EP - 56 JF - Journal of neurocytology JO - J. Neurocytol. VL - 33 IS - 5 N2 - A variety of studies indicate that spinal nicotinic acetylcholine receptors modulate the behavioral and autonomic responses elicited by afferent stimuli. To examine the location of and role played by particular subtypes of nicotinic receptors in mediating cardiovascular and nociceptive responses, we treated neonatal and adult rats with capsaicin to destroy C-fibers in primary afferent terminals. Reduction of C-fiber terminals was ascertained by the loss of isolectin B4, CGRP and vanilloid receptors as monitored by immunofluorescence. Receptor autoradiography shows a reduction in number of epibatidine binding sites following capsaicin treatment. The reduction is particularly marked in the dorsal horn and primarily affects the class of high affinity epibatidine binding sites thought to modulate nociceptive responses. Accompanying the loss of terminals and nicotinic binding sites were significant reductions in the expression of alpha 3, alpha 4, alpha 5, beta 2 and beta 4 nicotinic receptor subunits in the superficial layers of the spinal cord as determined by antibody staining and confocal microscopy. The loss of nicotinic receptors that follows capsaicin treatment results in attenuation of the nociceptive responses to both spinal cytisine and epibatidine. Capsaicin treatment also diminishes the capacity of cytisine to desensitize nicotinic receptors mediating nociception, but it shows little effect on intrathecal nicotinic agonist elicited pressor and heart rate responses. Hence, our data suggest that alpha 3, alpha 4, alpha 5, beta 2 and beta 4 subunits of nicotinic receptors are localized in the spinal cord on primary afferent terminals that mediate nociceptive input. A variety of convergent data based on functional studies and subunit expression suggest that alpha 3 and alpha 4, in combination with beta 2 and alpha 5 subunits, form the majority of functional nicotinic receptors on C-fiber primary afferent terminals. Conversely, spinal nicotinic receptors not located on C-fibers play a primary role in the spinal pathways evoking spinally coordinated autonomic cardiovascular responses. SN - 0300-4864 UR - https://www.unboundmedicine.com/medline/citation/15906161/Ablation_of_primary_afferent_terminals_reduces_nicotinic_receptor_expression_and_the_nociceptive_responses_to_nicotinic_agonists_in_the_spinal_cord_ L2 - http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=15906161.ui DB - PRIME DP - Unbound Medicine ER -