Effects of ocular blood flow changes on the efferent activity of cat ciliary nerves

The efferent activity of the short ciliary nerves was studied in 23 anesthetized cats. Spontaneous activity was recorded in all preparations, and 33% showed a rhythmic discharge. Ipsilateral common carotid occlusion (ICCO) at constant intraocular and arterial pressures changed the discharge frequency in 14 of 33 filaments. Of these, 13 filaments showed a decrease in their firing frequency whereas in only one the discharge increased. Contralateral common carotid occlusion (CCCO), at constant intraocular pressure, changed the firing frequency in 8 of 20 filaments: 5 of them showed a decrease in their discharge frequency, whereas in 3 of them the discharge increased. This occurred when systemic arterial pressure was allowed to increase. These results suggest the presence of an efferent pathway involved in the nervous modulation or control of intraocular blood flow, aqueous humor dynamics, and/or intraocular pressure.