The 24-hour ganglionectomy effect in rabbits: The influence of adrenergic blockade, adrenalectomy and carotid ligation

Abstract

The pharmacological response of the intraocular pressure and outflow facility in albino rabbit eyes to endogenous catecholamines released as a result of sympathetic denervation was studied by the manometric pressure-decay curve technique. The experiments were designed to test whether the 24-hr ganglionectomy effect (lowering of intraocular pressure and increase in outflow facility 24 hr after ganglionectomy) could be abolished by specific α- or β-adrenergic blocking agents, and whether blood-borne adrenal medullary hormone contributed to the ganglionectomy effect. Propranolol (the β-adrenergic blocking agent) failed to influence the ganglionectomy effect, whereas intravitreous phentolamine (α-adrenergic blocking agent) reduced it by about 50%. Adrenalectomy, with adrenal cortical replacement therapy, failed to diminish the ganglionectomy effect. It was concluded from these experiments that (1) β-adrenergic receptors were not involved in the outflow of aqueous humor, nor did they play a role in the ganglionectomy effect; (2) an α-adrenergic mechanism accessible via the aqueous circulation (such as the release of endogenous accounted for only a part of the ganglionectomy effect; and (3) circulating adrenal hormone did not enter the aqueous humor in quantities sufficient to affect outflow facility 24 hr after ganglionectomy. Reduction of blood flow to the denervated eye by means of ipsilateral common carotid artery ligation abolished the 24-hr increase in outflow facility usually observed.