The modification of the pupillary light reflex by chlorpromazine, diazepam, and pentobarbital

Abstract

Single light flashes or electrical stimulation of the optic nerve evoke a bi- or triphasic potential in the short ciliary nerves. The central conduction and transmission time (from the optic nerve to the emergence of the preganglionic autonomic oculomotor fibers) is estimated to be about 12 msec. After prior conditioning stimuli, evoked responses to subsequent test shocks are inhibited when the interval is between 15 and 30 msec. Recovery takes 120 msec or longer. This inhibitory period is prolonged by pentobarbital. CPZ, which constricts the pupil in man, enhances optically evoked ciliary potentials, whereas diazepam and pentobarbital decrease them. The CPZ effect is interpreted as a diminution of inhibitory influences on the pupilloconstrictor outflow.