[Neurotransmitter control of pupillary motoricity in man]

The pupillary responses to different agonists and antagonists of the sympathetic and parasympathetic systems have been studied in normal volunteers. The eyedrops were instilled unilaterally and the responses were evaluated by measuring the changes in diameter of the pupils (in millimeters). All the eyedrops induced an unilateral response on the instilled side. The mydriatic substances (phenylephrine, thropamide, tyramine) showed an evident and lasting action. Phenylephrine 1% was found to be a threshold dose to acquire the mydriatic effect. The beta blocking agent (timolol) induced a short mydriatic response, while methaproterenol did not change the pupillary diameter. Clonidine caused an unilateral mydriasis. The alpha blocking agent and the parasympathetic system stimulation agent induced miotic effects The results are discussed with particular reference to the possible mechanism of the pupillary response to timolol and clonidine.