Contractile response and amine receptor mechanisms in isolated middle cerebral artery of the cat

Abstract

On the basis of previous histochemical investigations demonstrating a rich adrenergic and cholinergic nerve supply to the main pial arteries, the contractile response of the feline middle cerebral artery to various vasoactive amines was studied in vitro. A 4 mm long segment of the artery was mounted in a rigid system allowing the registration of even very small circular contractions by a force-displacement transducer. The preparation was maintained in an aerated and thermostatically controlled (37° C) Krebs-Ringer buffer solution at pH 7.35–7.45. Dose-response curves are presented for 5-hydroxytryptamine, acetylcholine, histamine, adrenaline, noradrenaline and isoprenaline; a contractile response up to approximately 350 dyn being obtained. The contraction induced by 5-hydroxytryptamine, acetylcholine and histamine was blocked by the respective specific antagonists. From experiments with adrenergic blocking agents it was concluded that the catecholamine-induced contraction of the pial artery is mediated through a combination of alpha- and beta-adrenergic receptors.