Microinjeção de midazolam no hipotálamo posterior não reverte a antinocicepção induzida pelo labirinto em cruz elevado aberto em ratas
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 h...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/31790 |
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| Resumo: | 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. |
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