EVIDENCE FOR PURINERGIC INNERVATION OF THE ANOCOCCYGEUS MUSCLE

Abstract

Fluorescence histochemical localization of quinacrine (which binds to adenosine 5′‐triphosphate (ATP)) revealed nerve fibres running singly and in bundles in both rat and rabbit anococcygeus muscle. Single neurone cell bodies and ganglia containing between 2 and 50 cells were also observed. Catecholamine fluorescence studies revealed a dense adrenergic ground plexus, but no adrenergic ganglion cells were detected. No acetylcholinesterase‐positive nerve fibres or ganglion cells were seen in the rat. When the tone was raised with guanethidine, a relaxation in response to field stimulation was revealed, which was unaffected by atropine but blocked by tetrodotoxin. Release of ATP increased 3 to 6 times above background during stimulation of these non‐adrenergic, non‐cholinergic, inhibitory nerves. Neither quinacrine staining nor the release of ATP during inhibitory nerve stimulation was affected by 6‐hydroxydopamine treatment, which abolished catecholamine fluorescence. Exogenous ATP produced relaxation in high tone preparations of the rabbit anococcygeus muscle. ATP produced either contraction or a small relaxation followed by a contraction of the rat anococcygeus muscle, but treatment with low concentrations of the prostaglandin synthesis inhibitor indomethacin, converted the contraction to a relaxation. These data are consistent with the view that the anococcygeus muscle is innervated by purinergic inhibitory nerves. 1978 British Pharmacological Society