Differential effects of inhibitors of monoamine oxidase Types A and B on the adrenergic system of the rabbit iris.

Topical instillation of inhibitors of monoamine oxidase Types A and B into the rabbit eye, followed by the administration of a releaser of monoamines (Ro 4-1284), induces strong and sustained dilation of the iris. The mydriatic pattern differs markedly with A- and B-inhibitors and with the duration of the inhibitor treatment. The Type B inhibitor, deprenyl, prevents the degradation of exogenous 2-phenylethylamine and possibly of the endogenous amine X capable of releasing monoamines from a compartment less accessible to Ro-1284.