[Level of neuroactive steroids in the brain, and gender-related differences in formation and decrease of conditioned reflex in rats].

We investigated gender-related differences in dynamics of the brain sexual steroids during learning and the decrease of conditioned reflex in the modeling experiment. It was revealed that, before training to conditioned reflexes, females manifested a greater anxiety than males. Significant differences between males and females in formation of the conditioned reflex of passive avoidance were not revealed, whereas the conditioned response decrease were by 2-3 days faster in male rats than in females. It was revealed that there was an increase of testosterone content in various structures of the brain, especially in hippocampus and frontal cortex with its constant level in the blood plasma in learning conditioned response of passive avoidance in male adult rats. Also an increased estradiol concentration was found in females' amygdale, while increased value of estradiol was detected in hippocampus and the singular cortex in decrease of the conditioned response of passive avoidance. In blood plasma, the testosterone level was not changed, and the estradiol concentration was reduced significantly after the decreased conditioned reflex. Different dynamics of changes in the levels of sex steroids in the brain and the blood plasma can indicate a probability of their formation in nervous tissue. The correlation analysis confirms the conception about selective involvement of the brain's testosterone and estradiol in the specific structures in realization ofthe learning and memory processes in adult male and female rats.

[Sex-related peculiarities of conditioned reflex activity and dynamics of sex steroids in the brain].

Sexual peculiarities of dynamics of brain sex steroids in the process of learning and extinction of the conditioned reflex of passive avoidance have been studied in model experiment. Prior to learning of conditioned reflex, females were found to be distinguished by manifestation of anxiety and fear as compared with males. At formation of the conditioned reflex, no significant sex differences were detected between males and females, whereas extinction of the conditioned reaction of passive avoidance in rat males occurred by 2-3 days faster than in females. At learning of conditioned reaction of passive avoidance, in sexually mature rat males there was revealed an increase of the testosterone content in various brain structures, especially in hippocampus and frontal cortex, while its level in blood plasma remained unchanged. Also shown was an elevation of estradiol concentration in female amygdale, whereas at extinction of the conditioned reaction of passive avoidance, a rise of estradiol values was noted in hippocampus and cingular cortex. At the same time the testosterone level in blood plasma did not change, whereas the estradiol concentration decreased statistically significantly after extinction of the conditioned reflex. Different dynamics of changes of the sex steroid levels in brain and blood plasma can indicate a probability of their formation in the nervous tissue. The performed correlation analysis confirms the concept of selective involvement of testosterone and estradiol of specific brain structures in realization of the process of learning and memory in sexually mature rat males and females.

Interaction of total blood calcium levels and brain catecholamines during the formation and reinforcement of memory traces in hypoparathyroidism.

Interactions between the total blood calcium level and catecholamine contents in limbic brain structures during the formation and extinction of a conditioned passive avoidance reflex were studied in rats with hypoparathyroidism. Impairments of calcium support for the processes of conditioned reflex activity were seen after removal of the parathyroid glands. Animals with hypoparathyroidism not only showed changes in basal dopamine and noradrenaline levels in limbic structures, but also impairments of catecholamine dynamics during the acquisition and forced extinction of a conditioned passive avoidance reflex. These results demonstrate changes in the functional dynamics of the dopaminergic and noradrenergic systems of the brain in conditions of abnormal calcium homeostasis in the body, which underlie abnormalities of conditioned reflex activity and the acquisition of the adaptive behavioral strategies.

[Correlation between the levels of calcium in the blood and catecholamines in the brain during memory formation and fixation in hypoparathyreosis].

Relationship between the blood level of calcium and the level of catecholamines in the brain limbic structures was studied in passive avoidance conditioning and extinction in rats with hypoparathyreosis. After parathyroidectomy, conditioning processes were shown to be impaired as a result of a disorder of calcium supply. In hypoparathyreosis, not only the basic dopamine and noradrenalin levels change, but catecholamine dynamics in learning and forced extinction of a passive avoidance reaction shifts. The results point to the deranged functioning of dopamine and noradrenaline brain systems as a result of disorders in calcium homeostasis. These shifts result in disorders of conditioning and development of an adaptive behavioral strategy.