Effects of quipazine on blood pressure in pithed rats.

The effects of quipazine on blood pressure in pithed rats and the mechanism of the pressor response were studied. Quipazine and 5 HT produced an abrupt increase in blood pressure. The pressor responses were reduced by phentolamine and phenoxybenzamine. The noradrenaline depletion induced by pretreatment with reserpine significantly reduced the pressor effects of quipazine. Methysergide, at a dose which did not alter pressor responses to noradrenaline, reduced the increase in blood pressure induced by quipazine and 5 HT. These results suggest that quipazine activates 5-hydroxytryptaminergic receptors stimulating the release of noradrenaline. The effect observed in reserpinized rats can be explained by the interconnection of 5-hydroxytryptamine receptors and alpha-adrenoceptors.