The effects of chronic combined treatment with alpha7-nicotinic cholinergic receptor agonist RJR-2403 (1.0 mg/kg intraperitoneally) or alpha7-nicotinic cholinergic receptor antagonist mecamylamine (1.0 mg/kg intraperitoneally) and 17beta-estradiol (0.5 microg per rat intramuscularly) for 10 days on passive avoidance retention were studied in middle-aged (15 months) ovariectomized rats with experimental Alzheimer type dementia. Chronic treatment with RJR-2403 and 17beta-estradiol had a pronounced antiamnestic effect under conditions of Alzheimer type dementia in middle-aged ovariectomized rats.

The effects of L-tryptophan on conditioned reflex learning and behavior were studied in male rats with deficient and excess thyroid hormones levels. The learning process was studied using a model consisting of a conditioned active avoidance response; animal behavior was assessed in an open field test. These studies showed that in conditions of thyroid hormone deficiency. L-tryptophan had positive effects on the acquisition and reproduction of the active avoidance reflex, restoring the ability of the animals to learn actively; L-tryptophan increased investigative activity in the open field test. In conditions of increased thyroid hormone levels, L-tryptophan reversed the mild stimulating effects of thyroid hormones on the processes of developing and performing the active avoidance habit, and increased investigative activity, but decreased the amount of grooming.

We studied the effect of chronic administration of 5-HT(1A)-receptor agonist 8-OH-DPAT (0.05 mg/kg subcutaneously) or antagonist NAN-190 (0.1 mg/kg intraperitoneally) for 14 days on anxious-depressive-like behavior of female rats during the key phases of the estrous cycle. Chronic administration of NAN-190 during the estrus phase produced an anxiogenic effect, while its administration during proestrus phase induced an anxiolytic effect. Administration of 8-OH-DPAT had no effect on anxiety level, but produced a pronounced antidepressive effect irrespective of the phase of the estrous cycle.