AbstractSome acute pharmacological effects have been examined of racemic ADT 16 (1,2,3,5,6,11b-hexahydro[1]benzothieno[3,2-g]indolizine hydrochloride), on peripheral and central responses mediated by 5-HT and adrenergic systems in the rat. In-vitro, ADT 16(10–1000 Nm), similarly to mianserin, antagonized the inhibitory responses to B-HT 920 of the electrically-stimulated rat isolated prostatic vas deferens. High concentrations of ADT 16 (10 μm), also resembled those of mianserin by potentiating twitch responses to electrical stimulation of the tissue. Contractile responses to phenylephrine of rat isolated epididymal vas deferens were antagonized by ADT 16 (0·3–1 μm). In the rat stomach fundus strip, ADT 16 (1–3 μm) antagonized contractions due to 5-HT. ADT 16 (0·1–1 μm) had no effect on responses to acetylcholine of the guinea-pig isolated ileum. In-vivo, in spinalized, decerebrated rats, fenfluramine- or clonidine-induced facilitation of flexor reflex activity of the anterior tibialis muscle was attenuated by ADT 16 (3 and 10 mg kg−1, i.v., and 3 mg kg−1, i.v. respectively). In the anaesthetized rat, l-3,4-dihydroxyphenylalanine (l-dopa)- or l-5-hydroxytryptophan (l-5-HTP)-induced increases in the frequency of spontaneous twitches of the anterior digastricus muscle were attenuated by ADT 16 (1 and 3 mg kg−1, i.v.; n = 4). It is concluded that ADT 16, similarly to mianserin, is a novel peripherally and centrally active antagonist of 5-HT and adrenergic responses in the rat.
