Effects of benzodiazepines and pentobarbital on the evoked potentials in the cat brain

The sites of action of benzodiazepines, diazepam and ID-540 [7-chloro-5-(o-fluorophenyl)-1-methyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one) on the central nervous system were examined and compared with those of pentobarbital using evoked potentials recorded on the limbic system and hypothalamus in the cat brain. Benzodiazepines affected the various neuronal connections of the intra-limbic, limbic-hypothalamic and midbrain-limbic systems; especially the amygdala (AMYG)-, ventromedial hypothalamus (VMH)- and central gray matter (SGC)-hippocampal (HIPP) evoked potentials were attenuated, whereas the AMYG-VMH, VMH-AMYG and the septum (SP)-VMH evoked potentials were facilitated. Pentobarbital selectively attenuated the SGC-, VMH- and AMYG-HIPP evoked potentials, or facilitated the VMH-AMYG and the SP-HIPP evoked potentials. Both benzodiazepines and pentobarbital affected three afferent hippocampal neuronal connections, areas of the reticulo-hypothalamic systems regulating hippocampal activity, while only benzodiazepines affected the neuronal influence of the amygdaloid and septal areas on the hypothalamus.