Effect of superior cervical ganglion ectomy on the response to some drugs of rat iris dilator muscle

Abstract

We examined the effect of superior cervical ganglionectomy on the contractile response of dilator muscle of rat iris to norepinephrine (NE), methoxamine (Met), 5-HT and K+. The validity of the ganglionectomy was confirmed by the disappearance of catecholamine fluorescence and of transmural nerve stimulation induced-contraction of the dilator. The dose-response curve for NE was significantly shifted to the left (ca. × 10) 7 days after denervation, while those for Met, 5-HT and K+ were not. Cocaine did not further sensitize the denervated muscle to NE, although it sensitized the normal muscle to a similar extent as was caused by denervation. Sensitivity to Met was not affected in both control and denervated muscles by cocaine. The maximum response to these drugs was little affected or rather tended to be decreased. These results indicate that in the dilator muscle, the denervation causes specific supersensitivity to the transmitter in contrast to the specific plus nonspecific supersensitivity to cholinergic drugs observed in sphincter muscle and suggest that this supersensitivity results from an impairment of the neuronal uptake process after degeneration of the adrenergic nerve endings.