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In order to study the role of the lateral amygdala in the peptidergic mechanisms of stress resistance in rats, we measured the levels of beta-endorphin and substance P in the blood and hypothalamus of stress-resistant and stress-responding rats during emotional stress under conditions of a functional blockade of the basolateral amygdala by anodic polarization. Emotional stress was created by immobilization of rats within narrow chambers, with additional aperiodic electrocutaneous stimulation. It was found that lateral areas of the amygdala play an important role in the maintenance of stress-resistance mechanisms in rats. Their bilateral blockade decreased the resistance to stress. As well, in our experiment we found reciprocal relationships between blood plasma and hypothalamic levels of peptides (substance P and beta-endorphin) both in stress-resistant and stress-responding rats. Thus, peptidergic mechanisms of stress resistance are associated with functioning of the amygdala. [ABSTRACT FROM AUTHOR]

Prenatal administration of delta-sleep-inducing peptide (DSIP) at a high dose (120 μg per 100 g of body weight) and low dose (12 μg per 100 g of body weight) and prenatal emotional stress resulted in aggressive behavior of two-month-old male progeny of DD mice in the resident-intruder test. However, no increase in the aggressiveness of male progeny of the highly aggressive C57BL mice, which we studied previously, was observed. These data suggest that the prenatal effect of DSIP on the behavior of DD and C57BL mice depended on the individual genotype. The aggressiveness of two-month-old male progeny of the DD mice that were subjected to prenatal treatment with DSIP was accompanied by enhanced activity of monoamine oxidase A (MAO A) in the cerebral hemispheres. These results suggest that DSIP should be considered as a regulatory peptide that controls the expression of the MAO A gene, and that MAO A was probably involved in the development of aggressiveness of the male progeny of the DD mice after the prenatal administration of DSIP. Prenatal emotional stress had no significant influence on the activity of MAO A in the brain of two-month-old male progeny of DD mice. Development of the aggressiveness of two-month-old male progeny of DD mice which were produced by stressed mothers was possibly not associated with fluctuations in the activity of MAO A in the brain. [ABSTRACT FROM AUTHOR]