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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Nociceptive vocalization response in guinea pigs modulated by opioidergic, GABAergic and serotonergic neurotransmission in the dorsal raphe nucleus

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Author(s):
Ferreira, Mateus Dalbem [1] ; Menescal-de-Oliveira, Leda [1]
Total Authors: 2
Affiliation:
[1] Univ Sao Paulo, Fac Med Ribeirao Preto, Dept Physiol, BR-14049900 Ribeirao Preto, SP - Brazil
Total Affiliations: 1
Document type: Journal article
Source: Brain Research Bulletin; v. 106, p. 21-29, JUL 2014.
Web of Science Citations: 5
Abstract

The dorsal raphe nucleus (DRN) is involved in the control of several physiological functions, including nociceptive modulation. This nucleus is one of the main sources of serotonin to the CNS and neuromodulators such as opioids and GABA may be are important for its release. This study evaluated the influence of serotonergic, GABAergic and opioidergic stimulation, as well as their interactions in the DRN, on vocalization nociceptive response during a peripheral noxious stimulus application in guinea pigs. Morphine (1.1 nmol), bicuculline (0.50 nmol) and alpha-methyl-5-HT (1.6 nmol) microinjection on the DRN produces antinociception. The antinociception produced by morphine (1.1 nmol) and alpha-methyl-5-HT (1.6 nmol) into the DRN was blocked by prior microinjection of naloxone (0.7 nmol). The alpha-methyl-5-HT effect blocked by naloxone may indicate the existence of 5-HT2A receptors on enkephalinergic interneurons within the dorsal raphe. Pretreatment with muscimol (0.26 nmol) also prevented the antinociceptive effect caused by morphine (1.1 nmol) when administered alone at the same site, indicating an interaction between GABAergic and opioidergic interneurons. The antinociception produced by bicuculline (0.5 nmol) in the DRN was blocked by prior administration of 8-0H-DPAT (0.5 nmol), a 5-HT1A agonist. This may indicate that the 5-HT autoreceptor activation by 8-OH-DPAT at DRN effector neurons can oppose the bicuculline disinhibition effect applied to the same effectors. Thus, we suggest that 5-HT2 receptor activation in the DRN promotes endorphin/enkephalin release that may disinhibit efferent serotonergic neurons of this present structure by inhibiting GABAergic interneurons, resulting in antinociception. (C) 2014 Elsevier Inc. All rights reserved. (AU)