STUDIES ON THE DECENTRALIZED NICTITATING MEMBRANE OF THE CAT. I. EFFECT OF POSTGANGLIONIC ELECTRICAL STIMULATION ON THE RESPONSE TO EXOGENOUS CATECHOLAMINES

¹ Department of Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York

The effect of postgangliomc electrical stimulation and catecholamine infusions on the in vivo responses of the decentralized nictitating membrane of the cat to epinephrine and norepinephrine was investigated. The amplitude of the response of the decentralized membrane to norepinephrine was reduced during continuous submaximal postgangliomc electrical stimulation and after periods of intermittent supramaximal postganglionic electrical stimulation. These stimulation procedures did not affect the response of the normal membrane to norepinephrine. The response to epinephrine was little affected in amplitude, but the duration of the response was significantly reduced. Infusions of catecholamines did not affect the responses of the decentralized membrane to epinephrine or norepinephrine. Cocaine reduced poststimulation depression of the response to norepinephrine. The results suggest that, after decentralization, the potentiation of the responses of the nictitating membrane to catecholamines may be due, in part, to a reduction of the uptake of these substances into nerve terminals. Electrical stimulation of the postganglionic fibers which transiently reduced the response of the decentralized membrane to norepinephrine may be increasing the capacity of the decentralized nerve terminals to take up norepinephrine. Cocaine, which reduced the effect of electrical stimulation of the postganglionic fibers on responses of the decentralized membrane to norepinephrine, may be acting through its well known action of reducing uptake of norepinephrine.