Supraspinal interactions of anesthetic, neuroleptic and analeptic drugs on the fusimotor effects of pinna stimulation in the cat

Abstract

1. The various effects of neuroleptic, anesthetic and analeptic drugs were studied on the extensor-fusimotor response to pinna stimulation (PS) in decerebrate cats. 2. Chlorpromazine, in contrast to previously observed differential effects of i. v. anesthetics, depressed in a nonspecific manner the facilitatory as well as the inhibitory influences of the PS. This depressant effect of chlorpromazine on the fusimotor-influencing systems of the brain stem was independent of the later occurring fall in blood pressure. 3. Facilitatory PS-responses in decerebrate animals were changed to inhibitory ones by anesthetics. These inhibitory PS-responses were used to test the antagonistic-analeptic effects of bemegride and pentetrazol. 4. Bemegride regularly fully removed the inhibitory PS-response produced by barbiturates (pentobarbital sodium and butallylonal sodium), thus reversing it to facilitation. However, its counteraction against chloralose was only short and incomplete. 5. Pentetrazol also showed a strong antagonistic influence upon the barbiturate-induced alterations of the PS-response, although this was distinctly weaker than that of bemegride. Pentetrazol did not affect the chloralose-induced inhibitory PS-response at all. 6. The PS proved to be a comprehensive, effective and natural procedure to activate the brain stem reticular formation. Its descending fusimotor effects can give conclusive information about the experimentally altered functional condition of these structures. Therefore, the PS-method allows a simple testing of interfering effects of centrally acting drugs.