Contractile Responses to Endothelin in Feline Cortical Vessels in situ

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Abstract
In this study in chloralose-anaesthetised cats, the vasomotor responses of individual pial vessels on the cortical surface to perivascular subarachnoid microapplication of endothelin were examined. Endothelin (3 × 10−10-3 × 10−6 M) induced marked vasoconstriction of pial arterioles (-33.5 ± 3.8% at 3 × 10−6 M) and pial veins (-35.1 ± 2.7% at 3 × 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 m M) or alkalotic CSF (pH 7.48).