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The content of norepinephrine (NE) and serotonin (5-HT) in the right and left halves of the brain of rats was compared in the norm, during the development of defensive two-way avoidance conditioned reflexes (TWACR), and with the administration of peptides which influence learning and memory, namely desglycine-arginine vasopressin (DG-AVP), ACTH4-7 pro-gly-pro, and dalargin. These investigations demonstrated that the content of NE in the right cerebral hemisphere is significantly higher than in the cortex of the left. Significant differences were not detected with respect to the 5-HT content in symmetrical parts of the brain. The asymmetry of the NE content was eliminated under the influence of the development of the TWACR. The systemic administration of DG-AVP, ACTH4-7 pro-gly-pro, and dalargin essentially did not alter the 5-HT content, and decreased the NE content in the cortex and in the rest of the brain. In the process the NE content of the right and left hemisphere evened out. The data obtained point to the asymmetrical character of the action of the neuropeptides and to the greater resistance of the serotoninergic system of the brain to a functional load and the administration of peptides by comparison with the noradrenergic system.

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The experiments reported here show that animals with different levels of acquisition of a conditioned passive avoidance reflex retrieved the reflex differently on systematic testing over a period of 28 days. Animals with the highest and high levels of training reproduced the reflex stably. Animals with an intermediate level of training reproduced the reflex with significant variation. Convulsions induced by pentylenetetrazole (75 and 50 mg/kg. i.p.) resulted in amnesia. The amnestic effect of pentylenetetrazole convulsions depended on the ratio of the intensity of training and the intensity of the induction of convulsions. Reminding, provided by presentation of an unconditioned stimulus, removed the amnestic effect of the convulsive state. Training led to significant decreases in the parameters determining the severity of the convulsive state. The convulsive state was a dissociative state, as subconvulsive doses of pentylenetetrazole (30 mg/kg, i.p.) removed the amnestic effect of convulsive doses. The dissociated state was reproduced by pharmacological reminding of the state of anxiety and fear which was formed during training. A subcataleptic dose of haloperidol (0.25 mg/kg, i.p.) induced a state of fear and removed the amnestic effect of the convulsive state. The same dose of haloperidol improved retrieval of the reflex in animals with low levels of training, i.e., those in which retrieval hardly occurred in normal conditions.