Acute treatment with 5-HT3 receptor antagonist, tropisetron, reduces immobility in intact female rats exposed to the forced swim test

The effects of tropisetron, a 5-HT3 receptor antagonist, were evaluated in adult Fischer female rats exposed to the Forced Swim Test (FST). Rats selected on the days of proestrus or estrus was immersed in a cylinder of water for 2 consecutive days. Rats were exposed to the FST for 15 min on day 1 (pretest), followed by a 5-min session (test), 24 h later. The proestrous-estrous group consisted of rats that were exposed to the FST on their proestrous stage (pretest); then 24 h later the same rats were exposed to the FST on their estrous stage (test). Rats in the estrous-diestrous group were exposed to the FST on their estrous stage (pretest) and 24 h later on their diestrous stage (test). Rats were injected intraperitoneally with saline or 1.0 or 2.0 mg/kg tropisetron 30 min prior to exposure to the cylinder on the test day. Immobility, swimming, and struggling behaviors were scored for 5 min. There was a significant decline in immobility after treatment with 2.0 mg/kg tropisetron in both groups. In addition, a significant decline in swimming was observed in the estrous rats (proestrous-estrous group) after treatment with 2.0 mg/kg tropisetron. There were no significant effects of tropisetron on struggling in any groups examined.