ATP is released into the rabbit eye by antidromic stimulation of the trigeminal nerve

Antidromic stimulation of the trigeminal nerve produces an irritative response in the rabbit eye characterized by ipsilateral miosis, hyperemia, elevated intraocular pressure, and a disruption of the blood-aqueous barrier. The latter is a bilateral effect. The mediator or mediators involved in this response of the eye are unknown. Increased ATP levels in aqueous humor could be found after trigeminal stimulation. Treatment of rabbits with dipyridamole further increased ATP levels in aqueous humor after stimulation, confirming the findings of Holton that stimulation of sensory nerves causes a release of ATP. Intravitreal injections of ATP could not reproduce the ocular irritative response; however, an iridial hyperemia of long latency and an increase in aqueous humor protein levels were produced. The mechanism of this part of the reaction requires further study.