Corticosterone does not change open elevated plus maze-induced antinociception in mice |
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Authors: | Mendes-Gomes Joyce Miguel Tarciso Tadeu Amaral Vanessa Cristiane Santana Nunes-de-Souza Ricardo Luiz |
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Affiliation: | aPrograma de Pós-Graduação em Psicobiologia, FFCLRP – USP Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP, Brazil;bLab. Neuropsicofarmacologia, Faculdade de Ciências Farmacêuticas – UNESP Rod. Araraquara-Jaú, Km 01, CEP 14801-902 Araraquara, SP, Brazil;cPrograma Interinstitucional de Pós-Graduação em Ciências Fisiológicas, UFSCAR-UNESP Rod. Washington Luis, Km 235, CEP 13565-905 São Carlos, SP, Brazil;dUnidade Universitária de Ciências Exatas e Tecnológicas, UnUCET-UEG Br 153 n.3105 CEP: 75132-903 Anápolis, GO, Brazil |
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Abstract: | It has been demonstrated that the exposure of rodents to the standard elevated plus-maze (sEPM: 2 open and 2 enclosed arms) elicits defensive behavioral reactions and antinociception and also activates the hypothalamo-pituitary-adrenal (HPA) axis. We have recently reported that EPM-induced antinociception is particularly observed when rats and mice are exposed to a totally open EPM (oEPM: 4 open arms). Given that the oEPM seems to be a more aversive situation than the sEPM, we hypothesized that oEPM exposure would induce higher plasma levels of corticosterone than sEPM exposure in mice. In this study, we investigated the influence of exposure to eEPM (enclosed EPM: 4 enclosed arms), sEPM or oEPM on plasma corticosterone levels in mice, with or without prior nociceptive stimulation (2.5% formalin injection into the right hind paw). We also tested whether the nociceptive response in the formalin test and oEPM-induced antinociception are altered by adrenalectomy. Results showed that oEPM-exposed mice spent less time licking the injected paw than sEPM- and eEPM-exposed animals. All three types of EPM exposure increased plasma corticosterone when compared to the basal group, but sEPM- and oEPM-exposed mice showed higher corticosterone levels than eEPM-exposed mice. Prior nociceptive stimulation (formalin injection) did not enhance the plasma corticosterone response induced by the three types of EPM exposure. Indeed, formalin injection appeared to provoke a ceiling effect on plasma corticosterone concentration. Furthermore, neither the nociceptive response in the formalin test nor oEPM-induced antinociception was changed by adrenalectomy. Present results suggest that oEPM antinociception does not depend on corticosterone release in mice. |
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Keywords: | Anxiety Fear Different types of EPM Antinociception Formalin test Corticosterone Adrenalectomy Mice |
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