Responses of normal and denervated cat superior cervical ganglia to some stimulant compounds.

1. The effect of preganglionic denervation on the sensitivity of the cat superior cervical ganglion to close-arterial injections of some stimulant compounds in vivo has been studied.2. Ganglionic responses were assessed (a) by recording simultaneously ganglion depolarization and post-ganglionic nerve action potential discharges, and (b) by measuring the contractions of the nictitating membrane and applying a correction for the change in sensitivity of the membrane to noradrenaline.3. No change could be detected in the electrical responses of the ganglion to carbachol after denervation.4. Nictitating membrane recording suggested that denervation increased the response of the ganglion to acetylcholine, but had little effect on ganglionic sensitivities to carbachol, nicotine, tetramethylammonium or potassium chloride.5. It was concluded that the neurones of the superior cervical ganglion do not, in general, show any substantial change of sensitivity to cholinesterase-resistant stimulant compounds after denervation. The supersensitivity to acetylcholine is probably the result of a reduction of ganglionic acetylcholinesterase.