The action of central depressant drugs on the spontaneous discharge of action potentials in the superior cervical sympathetic trunk of the cat

Abstract

Spontaneous action potentials were recorded in strands dissected from the preganglionic superior cervical trunk of cats anaesthetised with ether and N 2O. The rate of discharge of spontaneous action potentials was reduced by 63.7% (S.E. ± 4.2, n=26), after 0.5 mg kg chlorpromazine i.v. A local anaesthetic action was insufficient to account for the reduction in rate which occurred and the reduction is probably due therefore to a centrally mediated action. Perphenazine, in a dose of l mg kg i.v. reduced the rate of discharge by 61.6% (± 7.3, n=7). Pentobarbitone reduced the rate of discharge by 66.4% (± 8.9, n=5) in a dose of 10 mg kg , i.v., but 2 mg kg had little or no effect. Results with hydroxyzine and benactyzine were variable. Hydroxyzine had no action in some experiments, but in others 2 mg kg , i.v. produced a reduction of from 25 to 70%. Benactyzine had little effect, the greatest reduction observed being only 28%. It was concluded that some tranquillizers reduce the rate of discharge in a preganglionic sympathetic nerve. This may be a contributory factor in producing their psychotropic effects in man.