Analysis of bradykinin receptor mediating relaxation of cat cerebral arteries in vivo and in vitro

Summary Bradykinin (BK), methionyl-lysyl-BK (M-L-BK) and des-Arg ⁹-BK produced, in decreasing potency, dose-related dilatations of the superficial pial arteries of the cat in vivo. The competitive, specific B₁-receptor antagonist, des-Arg ⁹-Leu⁸-BK was ineffective against BK-induced dilatations in this in vivo model.On the cat middle cerebral artery in vitro (but not the basilar artery), under resting tension and when contracted with 5-hydroxytryptamine (5-HT) or KCl, concentration related relaxations were produced by BK, M-L-BK, and des-Arg ⁹-BK, this being the order of relative potency of the three kinins.There was no increase in the sensitivity of either the middle cerebral or the basilar artery in vitro under resting tension or when contracted with 5-HT or KCl to BK or des-Arg ⁹-BK, concentration effect curves to which were produced at 2 h intervals over an 8 h period. The B₁-receptor antagonist des-Arg ⁹-Leu⁸-BK was ineffective against relaxations to BK or des-Arg ⁹-BK of the middle cerebral artery under resting tension or when contracted with 5-HT.The receptor mediating dilatation of the superficial pial arteries of the cat in vivo and relaxation of the middle cerebral artery in vitro to kinins is of the B₂-type. The cat basilar artery in vitro is relatively insensitive to the action of kinins and this is possibly due to an absence of receptors for kinins on this tissue.