EVIDENCE FOR PURINERGIC INNERVATION OF THE ANOCOCCYGEUS MUSCLE

Abstract

1 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. 2 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. 3 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. 4 Release of ATP increased 3 to 6 times above background during stimulation of these non-adrenergic, non-cholinergic, inhibitory nerves. 5 Neither quinacrine staining nor the release of ATP during inhibitory nerve stimulation was affected by 6-hydroxydopamine treatment, which abolished catecholamine fluorescence. 6 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. 7 These data are consistent with the view that the anococcygeus muscle is innervated by purinergic inhibitory nerves.