Microinjeção de midazolam no hipotálamo posterior não reverte a antinocicepção induzida pelo labirinto em cruz elevado aberto em ratas

• Ano de defesa: 2018
• Autor(a) principal: Santos, Dianny Alves dos Santos e
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Rio Grande do Norte; Brasil; UFRN; PROGRAMA DE PÓS-GRADUAÇÃO EM BIOLOGIA ESTRUTURAL E FUNCIONAL
• Palavras-chave em Português: Antinocicepção induzida pelo medo; Labirinto em cruz elevado; Ácido Gama Aminobutírico; Teste de formalina
• Link de acesso: https://repositorio.ufrn.br/handle/123456789/31790

Animals exposure to threatening situations (innate or learned nature) induces a set of species-specific defense behaviors, among them, antinociception. It has been shown that rodents exposed to the open elevated plus maze (four open arms, oEPM), an aversive situation, exhibit antinociception of high magnitude. However, the mechanisms involved in such antinociception have not yet been elucidated. The present study investigated if antinociception induced in female rats exposed to oEPM could be reversed by microinjection of midazolam into the posterior hypothalamus. Thus, female rats received a right unilateral cannula implant in the posterior hypothalamus. One to three days after the implantation of the cannula, the animals were manipulated and habituated to the experimental room for three days. On the day of the test, animals were submitted to the formalin test (2.5%, 0.05 mL) injected subcutaneously into plantar surface of the right hind paw and then the first test phase (5 minutes initial) was recorded in a glass vat. Fifteen minutes after formalin injection, the animals received microinjection of saline 0,9% or midazolam (5 nmol) into the posterior hypothalamus. Twenty-five minutes after the formalin injection, the animals were individually exposed to the closed or open EPM for recording the time spent on licking the formalin injected paw for 10 minutes (Phase 2: 25-35 minutes). During the second phase of the formalin test, the experiment was recorded through a computer-camera circuit for further behavior analysis and nociceptive response analysis. The results show oEPM induced antinociception in formalin injected female rats but this response was not reversed by microinjection of midazolam (5 nmol) in the posterior hypothalamus. However, for a more robust conclusion about the involvement of the posterior hypothalamus in the oEPM-induced antinociception, additional studies are required at different doses since the literature indicates that larger doses appear to have an effect on the posterior hypothalamus in animal models of fear-induced antinociception.