Cervical Sympathetic Stimulation in Monkeys and the Effects on Outflow Facility and Intraocular Volume: A Study in the East African Vervet (Cercopithecus Aethiops)

¹ Department of Physiology, Makerere University College, Kampala, Uganda, and the Department of Pharmacology, University of Uppsala Sweden., Department of Ophthalmology, University of California Medical Center, San Francisco

The effects of cervical sympathetic stimulation have been studied in monkeys with the use of supramaximal 1 msec, rectangular pulses at 10 per second. Stimulation resulted in a mean decrease in intraocular volume of 5.0 µl (presumably due to intraocular vasoconstriction). The two-level constant pressure infusion method has been used to estimate facility of outflow. A mean decrease in facility of 0.077 ± 0.022 µl min^-1 per millimeter Hg was observed on the stimulated side, representing a decrease of 10 to 20 per cent. The effect was not modified by a large systemic dose of atropine (1.0 mg. per kilogram) and could not be blocked by 10 mg. per kilogram of the alpha-adrenergic blocking agent, phentolamine, which blocked the pupillary response and the intraocular vasoconstriction. Experiments with the beta-adrenergic blocking agent, propranolol, were inconclusive. Facility was not significantly changed by section of the preganglionic sympathetic nerve. It has been postulated that the facility change is either due to an effect on the trabecular meshwork or on specialized adrenergic ciliary muscle fibers.