Experiments using the "illuminated site" and "threatening situation" avoidance tests on rats after preliminary intraperitoneal injection of monoamines, mediator amino acids, and their agonists and antagonists, followed by microinjection of the same combinations into the posterior hypothalamus revealed functional ambiguity in the neurochemical profile of this limbic brain formation in realization of the anxiety states of various genesis. Pharmacological analysis was performed after preliminary injection of various anxiosedative and anxioselective agents into the posterior hypothalamus. It was found that the antiaversive action of chloridiazepoxide, fenibut, and indoter is manifested only under conditions of dominating fear motivation and is mediated by a GABAergic mechanism in the posterior hypothalamus. The anxiolytic effect of campiron is manifested only under negative-stressor zoosocial impact conditions and is mediated by the serotoninergic profile of synaptic switching in this limbic brain formation.