Hypothalamic stimulation of preganglionic autonomic activity and its modification by chlorpromazine, diazepam and pentobarbital

The spontaneous and hypothalamically evoked discharge patterns of the preganglionic cervical sympathetic, splanchnic and vagal nerves have been described and discussed as potential indicators of central “autonomic tone” in cat. Chlorpromazine and diazepam, in i.v. doses of 0·3-3 mg/kg, generally reduced slightly spontaneous evoked impulse traffic in cervical sympathetic fibers, but markedly attenuated the electrical activity in splanchnic nerves. Vagal efferent activity was more subtly affected by these two agents. Pentobarbital (3–10 mg/kg i.v.) depressed spontaneous and evoked potentials in the sympathetic and vagal nerves. In addition, it prevented the poststimulatory inhibition observed in sympathetic nerves.