Ocular adrenergic nerves contribute to control of the circadian rhythm of aqueous flow in rabbits.

Aqueous flow was measured fluorophotometrically in New Zealand white rabbits after unilateral decentralization of the cervical ganglion or cervical ganglionectomy to determine the role of ocular adrenergic input in regulating the circadian rhythm of aqueous flow. Both surgical procedures decreased the rate of aqueous flow during the dark phase when flow is high. During the light phase when flow is low, cervical ganglionectomy increased aqueous flow; decentralization may have increased flow also, but the increases were not statistically significant. Aqueous flow was also measured in normal rabbits after topical application of timolol during the light or dark to determine whether beta-adrenergic receptors play a role in controlling the circadian rhythm of flow. Timolol produced a small reduction of the rate of aqueous flow when applied topically during the dark but not during the light. These results suggest that part of the increase of aqueous flow during the dark phase is produced by adrenergic input to the ciliary processes and that beta-adrenergic receptors mediate part of this increase.