engleski

Swim stress inhibits 5-HT2A receptor-mediated head twitch behaviour in mice

Abstract Rationale: Several studies have shown that swim stress lowers the convulsant potency of different convulsants. The involvement of alpha2- adrenoceptors has been proposed. Drugs active at alpha2-adrenoceptors are known to modulate the head twitch response, the behaviour supposedly mediated by 5-HT2A receptors. Objectives: We tested whether swim stress modulates the head twitch behaviour in mice and whether alpha2-adrenoceptors interfere with this effect. Methods: The mice were stressed (10 min swimming at 18-190C), and the head twitch response was produced by 5-hydroxytryptophan (5-HTP, the precursor of serotonin) or by 1-(2, 5-Dimethoxy-4-iodophenyl)-2-aminopropane (DOI, a selective 5-HT2 receptor agonist) administered IP before or after swimming. Yohimbine (a non-selective alpha2-adrenoceptor antagonist), idazoxan (a selective alpha2-adrenoceptor antagonist) and diazepam were also used. Results: Swim stress inhibited profoundly the 5-HTP-induced head twitch behaviour in mice. alpha2-Adrenoceptor antagonists and diazepam failed to counteract this effect. The head twitch behaviour produced by DOI given before or after stress was also inhibited. Repeatedly stressed mice had only a mild inhibition of the head twitch response. Conclusions: The results demonstrate that swim stress inhibits, by an alpha2-adrenoceptor unrelated mechanism, 5-HT2A receptor-mediated head twitch behaviour in mice, suggesting that this effect and swim stress-induced anticonvulsant effect are produced by two separate and independent mechanisms.

Swim stress; Head twitch behaviour; 5-HTP (5-Hydroxy-L-tryptophan); DOI (1-(2; 5-Dimethoxy-4-iodophenyl)-2-aminopropane); alpha2-adrenoceptor antagonists; Diazepam

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