SEROTONERGIC MODULATION OF EYE BLINKS IN CAT AND MONKEY

Serotonergic modulation of spontaneous and reflexive blinking was stud ied in four cats and one monkey. In cats, facial nucleus injections of the type-2 serotonin receptor (5-HT2) antagonist ketanserin tended to increase the latency of the first (R-1) and second (R-2) components o f the blink reflex to supraorbital nerve stimulation. Injections of se rotonin tended to increase and of ketanserin, to decrease the duration and amplitude of R2. Serotonin also produced unilateral blepharospasm and hemifacial spasm. In the monkey, the 5-HT2 agonist 2,5-dimethoxy- 4-iodoamphetamine increased spontaneous blink frequency while ketanser in decreased both peak blink velocity and spontaneous blink frequency. These findings in cat and monkey indicate that serotonergic innervati on of the facial nucleus has a behaviorally important role in modulati on of spontaneous and reflexive blinks and suggest that dysfunction of serotonergic systems could be important to the pathophysiology of som e cases of blepharospasm. (C) 1998 Elsevier Science Ireland Ltd. All r ights reserved.