[Angiotensin II as a factor inhibiting the fear response].

Angiotensin II being administered into the rabbit lateral cerebral ventricles (0.015-0.15 micrograms) suppressed the fear response to electrical stimulation of the hypothalamic ventromedial nucleus, and in doses 1-10 ng blocked the inherent behavioral fear responses in rats. Microiontophoretic application of the same drug to cortex and parafascicular thalamic complex induced mainly an activation. Prevalence of inhibitory neuronal responses to angiotensin II was observed in the hypothalamic structures as well as in the midbrain RF. Cortical and subcortical neuronal responses to angiotensin II were enhanced after stimulation of the hypothalamic "fear center". The suppression of the fear response after angiotensin II administration seems to be related to changes in the cortical-subcortical interrelationships: diminishing of the midbrain RF ascending activation due to descending cortical effects.