An investigation of presynaptic alpha-adrenoceptor subtypes in the pithed rat heart.

1 The presynaptic cardio-inhibitory and postsynaptic pressor responses to the alpha-adrenoceptor agonists xylazine and cirazoline, and the interaction with the antagonists yohimbine and prazosin, were examined in the pithed rat.2 Evidence was found to suggest that, as well as the already established pre- and postsynaptic alpha(2)- and postsynaptic alpha(1)-receptors, presynaptic alpha(1)-receptors are present.