Antidepressant-Like Effect of Tetramethylpyrazine in Mice and Rats

The aim of this study was to investigate the potential antidepressive-like effect of tetramethylpyrazine (TMP), one of available blood-activating and stasis-eliminating components from traditional Chinese medicines, and its mechanism of the antidepressant-like action. Forced-swimming, tail-suspension, reserpine-induced hypothermia, akinesia and ptosis, 5-hydroxytryptophan (5-HTP)-induced head-twitch, and potentiation of noradrenaline (NE) toxicity tests, were per-formed to assess the potential antidepressant-like activity of TMP and to study the mechanism by which TMP exerts the antidepressant-like action. Intragastric (ig) administration of TMP markedly reduced the duration of immobility during forced-swimming tests and tail-supension test in rats and mice. TMP partialy reversed reserpine-induced hypothermia, ptosis and akinesia, and potentiated NE toxicity in mice, and these are similar to those of clomipramine; however, TMP did not potentiate 5-HTP-induced head-twitch response (HTR) in mice, and this is different from that of fluoxetine (FLU). The present data provide evidences that TMP possesses potent antidepressant-like activity, and it might be an adrenergic component of pharmacological activity, and its mechanism of antidepressant-like action is similar to that of clomipramine, and different from that of FLU.