Cholinergic Sensitivity: Normal Variability as a Function of Stimulus Background

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Science  07 May 1971:
Vol. 172, Issue 3983, pp. 583-585
DOI: 10.1126/science.172.3983.583


The sensitivity of the normally innervated iris sphincter to its neuro-transmitter, acetylchloline, and to relatd agents varies inversely with the preexisting physiological stimulus background, that is, the environmental light intnsity. This normal variability suggests the existence of a negative feedback mechahnism whereby sensitivity of the effector cell is modutlated by a product of neuronal activity.