Activation of 5-HT2C receptors in the dorsal periaqueductal gray increases antinociception in mice exposed to the elevated plus-maze

Author(s)

Baptista, Daniela ^{[1, 2]} ; Nunes-de-Souza, Ricardo Luiz ^{[3, 4, 2]} ; Canto-de-Souza, Azair ^{[4, 1, 2, 5]}

Affiliation

^[1] CECH UFSCar, Dept Psychol, Psychobiol Grp, BR-13565905 Sao Carlos, SP - Brazil

^[2] UNESP, Joint Grad Program Physiol Sci UFSCar, BR-13565905 Sao Carlos, SP - Brazil

^[3] Univ Estadual Paulista, UNESP, Sch Pharmaceut Sci, Pharmacol Lab, BR-14801902 Araraquara, SP - Brazil

^[4] Univ Sao Paulo, Inst Neurosci & Behav IneC, BR-14040901 Ribeirao Preto, SP - Brazil

^[5] Joint Grad Program Psychol UFSCar, BR-13565905 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Behavioural Brain Research; v. 235, n. 1, p. 42-47, NOV 1 2012.
• Web of Science Citations: 8

Abstract

Several findings have pointed to the role of the dorsal periaqueductal gray (dPAG) serotonin 5-HT1A and 5-HT2(A-C) receptor subtypes in the modulation of defensive behavior in animals exposed to the elevated plus-maze (EPM). Besides displaying anxiety-like behavior, rodents also exhibit antinociception in the EPM. This study investigated the effects of intra-dPAG injections of 5-HT1A and 5-HT2B/2C receptor ligands on EPM-induced antinociception in mice. Male Swiss mice received 0.1 mu l intra-dPAG injections of vehicle, 5.6 and 10 nmol of 8-OHDPAT, a 5-HT1A receptor agonist (Experiment 1), or 0.01, 0.03 and 0.1 nmol of mCPP, a 5-HT2B/2C receptor agonist (Experiment 2). Five minutes later, each mouse received an intraperitoneal injection of 0.6% acetic acid (0.1 ml/10 g body weight; nociceptive stimulus) and was individually confined in the open (OA) or enclosed (EA) arms of the EPM for 5 min, during which the number of abdominal writhes induced by the acetic acid was recorded. While intra-dPAG injection of 8-OHDPAT did not change open-arm antinociception (OAR). mCPP (0.01 nmol) enhanced it. Combined injections of ketanserin (10 nmol/0.1 mu l), a 5-HT2A/2C receptor antagonist, and 0.01 nmol of mCPP (Experiment 3), selectively and completely blocked the OAR enhancement induced by mCPP. Although intra-dPAG injection of mCPP (0.01 nmol) also produced antinociception in EA-confined mice (Experiment 2), this effect was not confirmed in Experiment 3. Moreover, no other compound changed the nociceptive response in EA-confined animals. These results suggest that the 5-HT2C receptors located within the PAG play a role in this type of environmentally induced pain inhibition in mice. (c) 2012 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 09/17938-6 - Role of serotonergic receptors of periaqueductal gray on antinociception of mice confined to open arms the elevated plus-maze
• Grantee: Daniela Baptista de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)