Pharmacological mechanism in slip-down behavior of mice

Slip-down from a raised platform was previously found in mice treated with morphine, and this behavior was also recognized in mice treated with a monoamine releaser methamphetamine. Pharmacological examination on the slip-down indicated that the behavior was induced by receptor stimulations by D-2 agonist PPHT and 5HT-2 agonist DOI. In mice treated with PPHT, antagonists of D-2, alpha(2), 5HT-2 and opiold mu. and kappa suppressed the behavior. In mice treated with DOI, antagonists of D-1, alpha(2), 5HT-1A, 5HT-3 and oploid mu and delta suppressed the behavior. These present findings suggest that the slip-down was mainly induced by opioid mu receptor activity regulated with monoamine activities. When the slip-down is considered as an anxious behavior, it may be also suggested that the anxiety induced by 5-HT activities furthermore stimulated the behavior via the other opiold receptor activities. (C) 2003 Tohoku University Medical Press.