The Pharmacology of the Eye During Denervation
By ‘denervation’ is meant interruption of a nerve pathway at or behind the last neuron. The interruption may be carried out surgically, such as by ganglionectomy of the superior cervical ganglion, or pharmacologically. When the nerve pathway is interrupted before the ganglion, one speaks of ‘decentralization’. Two weeks after denervation the effector cell develops increased sensitivity to directly acting agonists of the transmitter substances: noradrenaline for the sympathetic nervous system and acetylcholine for the parasympathetic nervous system. Indirectly acting agonists, in contrast, have less or no effect on the effector cell after denervation (Burn et al., 1931). The first phenomenon is called hyper- or supersensitivity while the second is called subsensitivity. Agonists which exert their effect by releasing the transmitter from the nerve endings are called indirectly acting agonists and affect the effector cell via the last neuron; the directly acting agonists act on the effector cell itself. Trendelenburg (1963) considers this distinction between direct and indirect action to be too extreme and postulates that the agonists of the transmitter substances fluctuate between these two poles in their action.
KeywordsEffector Cell Intraocular Pressure Nerve Ending Superior Cervical Ganglion Nictitate Membrane
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