CONTRACTILE RESPONSES TO ENDOTHELIN IN FELINE CORTICAL VESSELS INSITU

In this study in choralose-anesthetized cats, the vasomotor responses of individual pial vessels on the cortical surface to perivascular subarachnoid microapplication of endothelin were examined. Endothelin (3 x 10-10-3 x 10-6 M) induced marked vasoconstriction of pial arterioles (-33.5 ± 3.8% at 3 x 10-6 M) and pial veins (-35.1 ± 2.7% at 3 x 10-6 M). The concentration of endothelin inducing half-maximal response was in the nanomolar range, with pial veins being slightly more sensitive to the peptide than pial arterioles. Vasoconstrictions induced by endothelin were extremely prolonged, persisting for ~90 min after a single microapplication. Arterioles constricted by endothelin remained responsive to perivascular microapplication of K+ (10 mM) or alkalotic CSF (pH 7.48).