Vasoconstriction produced in the iris-ciliary body of the cat eye by stimulation of local ganglion-like receptors.

The presence of local ganglion-like receptors in the anterior segment of the cat eye was demonstrated in an isolated, arterially perfused preparation. The administration of the known ganglionic stimulants, acetylcholine (Ach) plus eserine, pilocarpine, and dimethylphenylpiperazinium bromide (DMPP) produced a vasconstriction. The actions of these stimulants were abolished by a-adrenergic blockade. Hexamethonium completely blocked the response to DMPP, was always ineffective as a blocking agent against Ach plus eserine, and sometimes abolished the response of pilocarpine. High concentrations of atropine always blocked the response to the three stimulant drugs. The data presented are also compatible with the currently accepted hypothesis of dual excitatory receptor sites on sympathetic ganglia.