Ethopharmacological analysis of the open elevated plus-maze in mice

Role of TRPV1 channels of the dorsal periaqueductal gray in the modulation of nociception and open elevated plus maze-induced antinociception in mice

“…EPM-or oEPM-induced antinociception has been previously reported in several studies [e.g. [30][31][32][33][41][42][43]48,49]. Corroborating these findings, the present results showed that mice exposed to the oEPM displayed an intense reduction of the time spent licking the paw injected with formalin solution, indicating marked antinociception.…”

“…Although no experiments in this regard have been performed, it is possible to suggest that our results reflect an elevation of endovanilloid levels (possibly AEA) in mice dPAG, since capsazepine attenuated oEPM-induced antinociception. Therefore, it seems that while exposure to sEPM would not recruit endovanilloid release within the PAG, the oEPM, as a potentially more aversive situation than the sEPM [42,43], would lead to TRPV1 activation within this limbic midbrain structure. This assumption is supported by previous results showing that (i) the magnitude of the antinociceptive response is higher in oEPM-than in sEPMexposed animals [30,42]; (ii) an ethopharmacological analysis of the mouse oEPM revealed that while the defensive behaviors were markedly attenuated by systemic administration of alprazolam, only marginal effects were observed with diazepam [43].…”

“…Therefore, it seems that while exposure to sEPM would not recruit endovanilloid release within the PAG, the oEPM, as a potentially more aversive situation than the sEPM [42,43], would lead to TRPV1 activation within this limbic midbrain structure. This assumption is supported by previous results showing that (i) the magnitude of the antinociceptive response is higher in oEPM-than in sEPMexposed animals [30,42]; (ii) an ethopharmacological analysis of the mouse oEPM revealed that while the defensive behaviors were markedly attenuated by systemic administration of alprazolam, only marginal effects were observed with diazepam [43]. Given that alprazolam is pharmacologically more potent than diazepam [56,57] and that diazepam produces robust anti-anxiety effects in sEPM-exposed rodents (e.g.…”

“…They were similarly constructed but comprised either four enclosed arms (eEPM) or four open arms (oEPM). These two sEPM-derived mazes were used in several experiments performed in our laboratory and showed to be more (oEPM) and less (eEPM) aversive compared to the standard maze [41][42][43].…”

Differential behavioral and molecular alterations upon protracted abstinence from cocaine versus morphine, nicotine, THC and alcohol

“…Morphine abstinent animals explored the open arms more than saline counterparts in the EPM test, pointing conversely to reduced anxiety. Head-dipping frequency and duration, however, were not concomitantly increased, as expected in mice with low levels of anxiety (Sorregotti et al, 2013). These results evoke a mu opioid receptor (MOR)-mediated mechanism, as similar discrepancies are observed in mice lacking MORs (Becker et al, 2014; Filliol et al, 2000; Ide et al, 2010), and rats injected with a MOR antagonist in the CeA (Wilson and Junor, 2008).…”