The effects of some centrally acting drugs on ganglionic transmission in the cat.

Transmission through the cat superior cervical ganglion was studied by recording the response of the nictitating membrane to both pre- and postganglionic cervical sympathetic nerve stimulation. The intra-arterial injection of central depressant drugs to the ganglion through the lingual artery depressed transmission through the ganglion. The central depressant drugs tested were (in decreasing order of activity): amylobarbitone, pentobarbitone, carbromal, benactyzine, mephobarbitone, hydroxyzine, phenobarbitone, azacyclonol, methylpentynol carbamate, paraldehyde, phenytoin, mephenesin, chlorbutol, troxidone, methylpentynol and barbitone. All were weaker ganglion-blocking agents than tetraethylammonium. The intra-arterial injection of the central stimulant drugs leptazol, bemegride, amiphenazole and 5-(1,3-dimethylbut-2-enyl)-5-ethylbarbituric acid (McN 481) also depressed ganglionic transmission. Leptazol or bemegride did not antagonize the ganglion-blocking action of amylobarbitone or troxidone. The intra-arterial injection of pecazine and perphenazine, and the intravenous injection of barbitone, benactyzine, azacyclonol, hydroxyzine, mephenesin, methylpentynol and paraldehyde impaired the response of the nictitating membrane to both post- and preganglionic stimulation. The implications of these observations are discussed.