Endogenous opiate analgesia induced by tonic immobility in guinea pigs

Autor(es)

C.R.A. Leite-Panissi ^[1] ; C.L. Rodrigues ^[2] ; M.R. Brentegani ^[3] ; L. Menescal-de-Oliveira ^[4]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

^[2] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

^[3] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

^[4] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Medical and Biological Research; v. 34, n. 2, p. 245-250, 2001-02-00.

Resumo

A function of the endogenous analgesic system is to prevent recuperative behaviors generated by tissue damage, thus preventing the emission of species-specific defensive behaviors. Activation of intrinsic nociception is fundamental for the maintenance of the behavioral strategy adopted. Tonic immobility (TI) is an inborn defensive behavior characterized by a temporary state of profound and reversible motor inhibition elicited by some forms of physical restraint. We studied the effect of TI behavior on nociception produced by the formalin and hot-plate tests in guinea pigs. The induction of TI produced a significant decrease in the number of flinches (18 ± 6 and 2 ± 1 in phases 1 and 2) and lickings (6 ± 2 and 1 ± 1 in phases 1 and 2) in the formalin test when compared with control (75 ± 13 and 22 ± 6 flinches in phases 1 and 2; 28 ± 7 and 17 ± 7 lickings in phases 1 and 2). In the hot-plate test our results also showed antinociceptive effects of TI, with an increase in the index of analgesia 30 and 45 min after the induction of TI (0.67 ± 0.1 and 0.53 ± 0.13, respectively) when compared with control (-0.10 ± 0.08 at 30 min and -0.09 ± 0.09 at 45 min). These effects were reversed by pretreatment with naloxone (1 mg/kg, ip), suggesting that the hypoalgesia observed after induction of TI behavior, as evaluated by the algesimetric formalin and hot-plate tests, is due to activation of endogenous analgesic mechanisms involving opioid synapses. (AU)

• Processo FAPESP: 97/14286-9 - Envolvimento do núcleo central da amígdala na modulação da imobilidade tônica, da antinocicepção e a participação da conexão funcional com a substância cinzenta periaquedutal em cobaias
• Beneficiário: Christie Ramos Andrade Leite Panissi
• Modalidade de apoio: Bolsas no Brasil - Doutorado