LOCUS OF THE ADRENERGIC BLOCKING ACTION OF DIBENAMINE

¹ Department of Pharmacology, University of Utah School of Medicine, Salt Lake City, Utah

Quantitative studies of the inhibition by Dibenamine of the response of the cat nictitating membrane to electrical cervical sympathetic nerve stimulation, and of the response of the chronically denervated nictitating membrane to various sympathomimetic and other agents (histamine, methacholine), have indicated that:

1. Dibenamine does not prevent the free penetration of sympathomimetic agents to their site of action.

2. Dibenamine in blocking doses does not paralyze the contractile mechanism of smooth muscle cells as shown by a normal response to non-sympathomimetic agents.

The mechanism of action of Dibenamine is discussed. Tentative explanations are offered for its long duration of action and for its failure to block completely the response of the nictitating membrane to nerve stimulation despite complete abolition of the response to circulating epinephrine and sympathin.