Centrally mediated hypotensive activity of B-HT 933 upon infusion via the cat's vertebral artery

The acute hypotensive and bradycardic effects of the new compound B-HT 933 (2-amino-6-ethyl-4,5,7,8-tetrahydro-6H-oxazolo-[5,4-d]-azepin-dihydrochloride) were investigated in anaesthetized cats and rats. In spite of the molecular structure of B-HT 933, which differs considerably from that of clonidine, its cardiovascular reaction pattern is comparable, although the former is much less potent. B-HT 933 showed a central nervous origin for its acute hypotensive action in anaesthetized cats, since its effects on blood pressure after infusion via the left vertebral artery were much greater than after intravenous application of the same amounts. Pretreatment with the alpha-adrenoceptor-blocking drug, piperoxan (100 micrograms/kg), completely abolished the hypotensive response to B-HT 933 (30 micrograms/kg) injected subsequently via the left vertebral artery. It is concluded that B-HT 933 is a centrally acting hypotensive drug. Central alpha-adrenoceptors are involved in a similar manner as the mechanism of clonidine.