Effects of an alpha-2 adrenoceptor antagonist, Org 3770, upon the autonomic function of the pupil

The effects of a single oral dose of an alpha‐2 adrenoceptor antagonist, Org 3770 (30 mg), upon the autonomic function of the human pupil have been investigated in six volunteers. Org 3770 reduced pupil diameter, possibly as a result of its alpha‐2 adrenoceptor blocking activity. Org 3770 did not reduce the mydriatric effect of phenylephrine and tyramine, nor was the miotic response to pilocarpine affected. These results are consistent with a blockade by Org 3770 of central alpha‐2 adrenoceptors.