[Effect of a decrease in the concentration of serotonin in the brain on elaboration and preservation of defensive conditioned reflexes].

Injection of a total dose of 1200 mg/kg of parachlorphenylalanine to mice leads to a 75% drop in the serotonin (5-OT) content in the brain with a subsequent return to the initial level in seven days. The processes of elaboration and reproduction of conditioned defensive active and "passive" avoidance reflexes were studied against the background of reduced 5-OT content. It has been assumed that the observed disturbances in elaboration are linked to the increased fear emotion when the mice are placed in new surroundings. Disturbances in retention of the "passive" avoidance conditioned reflex are in fact disturbances of its reproduction. A conclusion has been drawn that a drop in the 5-OT content in the brain does not prevent the formation and fixation of defensive temporary connections.