Trifluoperazine antagonizes postsynaptic alpha 1-but not alpha 2-adrenoceptor-mediated pressor responses in the rat

The specificity of the alpha-adrenergic blockade by trifluoperazine was tested in pithed rats. Trifluoperazine reduced the pressor effects of (-)-noradrenaline. The log dose-response curve to methoxamine, an alpha 1-agonist, was shifted to the right whereas the vasopressor responses to BHT-920, an alpha 2-agonist, were unaffected by trifluoperazine. It was concluded that trifluoperazine acts as a peripheral vascular alpha 1-antagonist in the rat.