Ventrolateral periaqueductal gray lesion attenuates nociception but does not change anxiety-like indices or fear-induced antinociception in mice

Author(s)

Mendes-Gomes, Joyce ^{[1, 2]} ; Santana Amaral, Vanessa Cristiane ^{[2, 3]} ; Nunes-de-Souza, Ricardo Luiz ^[2]

Affiliation

^[1] USP, FFCLRP, Programa Posgrad Psicobiol, BR-14040901 Ribeirao Preto, SP - Brazil

^[2] UNESP, Lab Neuropsicofarmacol, Fac Ciencias Farmaceut, BR-14801902 Araraquara, SP - Brazil

^[3] UNESP, UFSCAR, Programa Interinst Posgrad Ciencias Fisiol, BR-13565905 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Behavioural Brain Research; v. 219, n. 2, p. 248-253, JUN 1 2011.
• Web of Science Citations: 11

Abstract

The exposure of rodents to an open elevated plus-maze (oEPM: four open arms raised from the floor) elicits naloxone-insensitive antinociception. Midazolam infusion into the dorsal portion of the periaque-ductal gray (dPAG), a structure of the descending inhibitory system of pain, failed to alter oEPM-induced antinociception. Chemical lesion of dorsomedial and dorsolateral PAG attenuated defensive behavior in the standard EPM (sEPM), an animal model of anxiety, but failed to change oEPM-induced antinociception. The present study investigated the effects of bilateral lesion, with the injection of NMDA (N-methyl-D-aspartic acid), of the ventrolateral column of PAG (vIPAG) (i) on nociceptive response induced by 2.5% formalin injected into the right hind paw (nociception test) in mice exposed to the enclosed EPM (eEPM: four enclosed arms - a non-aversive situation) or to the oEPM and (ii) on anxiety indices in mice exposed to the sEPM without prior formalin injection. Results showed that oEPM-induced antinociception was not altered by lesion of vIPAG. Nevertheless, the lesion reduced the nociceptive response in mice exposed to the eEPM and increased general locomotor activity during the eEPM and oEPM exposure. Furthermore, vIPAG lesion did not alter anxiety-like indices in mice exposed to the sEPM. The results suggest that vIPAG does not play a role in oEPM-induced antinociception or in defensive reactions assessed in the sEPM. Moreover, vIPAG inactivation induces pain inhibition in mice not exposed to an aversive situation and seems to increase general activity. (C) 2011 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 05/01988-3 - Role of dorsal and ventrolateral portions of the periaqueductal gray in the modulation of defensive behaviors and antinociception induced by aversive situations in mice
• Grantee: Joyce Mendes Gomes Tessari
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)