| Abstract: | 1 A partially purified material has been isolated from methanol extracts of the bovine retractor penis muscle. This material exerts biological activity only after treatment with acid and subsequent neutralisation. The active principle in this extract, which appears to be no known autacoid, mimics the response to stimulation of the non-adrenergic, non-cholinergic nerves in the bovine isolated retractor penis muscle. 2 This inhibitory extract did not alter the heart rate or blood pressure of the anaesthetized rat when administered either by intravenous or intra-arterial injection, nor did it have any obvious effect on isolated cardiac muscle. 4 The extract produced relaxation of spiral strips of various arteries isolated from ox, cat, rabbit or rat, in which tone was induced by noradrenaline, K+ of Ba2+. 5 The extract also produced dilatation of the resistance vessels of the rat isolated mesenteric circulation and the rat hindquarters perfused with Krebs solution; tone was induced in these vessels by adrenaline or noradrenaline. 6 Lack of vasodilator activity of the extract in the whole animal appeared to be due to rapid inactivation in the blood, probably by binding to the erythrocytes. |
