An analysis of the pressor responses to putative alpha 1 and alpha 2-adrenoreceptor agonists given intravenously to conscious rabbits.

The selectivity of a range of alpha 1 and alpha 2-adrenoreceptor agonists was examined in the conscious rabbit. In this preparation the pressor responses to BHT 920, BHT 933, guanabenz and alpha-methylnoradrenaline were attenuated by idazoxan but not by prazosin. The pressor responses to clonidine and noradrenaline were attenuated by both idazoxan and prazosin while the response to phenylephrine was only significantly attenuated by prazosin. Both an immediate pressor response and a later depressor response to clonidine was observed but there were no depressor components to either BHT 920 or BHT 933 responses. Pressor responses to guanabenz were attenuated on repeated dosing.