THE EFFECT OF DENERVATION ON THE SENSITIVITY OF THE SUPERIOR CERVICAL GANGLION OF THE PITHED CAT

¹ Department of Pharmacology, University of Illinois at the Medical Center, Chicago, Illinois

The effect of denervation on the sensitivity of the superior cervical ganglion (SCG) to acetylcholine (ACh), carbachol, McN A-343 and K⁺ was studied in pithed cats. Both SCG were denervated 2, 4, 7 or 14 days prior to the experiment. On the left side sensitivity changes of the nictitating membrane were evaluated from frequency-response curves to supramaximal stimulation of the postganglionic nerve. On the right side nictitating membrane contractions were recorded after close i.a. injection of ganglionic stimulants. The nicotinic response to ACh was studied 30 min after pretreatment with diisopropylfluorophosphate and methscopolamine. While the sensitivity of the nictitating membrane to nerve stimulation increased with time after denervation, the ED5O of ACh for producing contractions of the nictitating membrane via ganglionic stimulation was unchanged. Thus, the actual sensitivity of the SCG to the nicotinic action of ACh appeared to be gradually decreasing over this time period. By the same criteria the sensitivity of the SCG to the stimulant actions of carbachol, McN A-343 and K⁺ was also decreased 2 weeks after denervation of the ganglion. The results are consistent with the hypothesis that the sensitivity of the SCG to ganglionic stimulants is depressed nonspecifically by chronic denervation.