Central Nervous System and Peripheral Mechanisms in Ocular Hypotensive Effect of Cannabinoids

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Abstract
• Systemic administration of cannabinoids decreases intraocular pressure (IOP). To determine whether the mechanism of action originates in the central nervous system, we administered various cannabinoids into the cerebral ventricles of conscious New Zealand albino rabbits. When Δ9-tetrahydrocannabinol (Δ9-THC), Δ8-tetrahydrocannabinol, cannabinol, and cannabidiol were given intravenously, only Δ9-THC produced dose-dependent ocular hypotension and miosis. Bolus administration into the cerebral ventricles or ventriculocisternal perfusion of Δ9-THC did not change IOP or pupil size. In urethane-anesthetized rabbits, IOP and blood pressure were lowered by intravenous administration of Δ9-THC but not by bolus cerebral administration. These observations indicate that the action of cannabinoids on IOP does not originate in the central nervous system. Alteration of blood pressure may be involved in the mechanism of ocular hypotension induced by Δ9-THC.