Cerebral ventricle-brain ratio in monozygotic twins discordant and concordant for schizophrenia

The influence of tetrapeptide tuftsin (Tyr-Lys-Pro-Arg) on learning, exploratory activity, emotional behavior, and hypothalamic monoamine content was studied in Wistar rats with different resistance to stress induced by acoustic stimuli. Positive effects of taftsin were more pronounced in low-resistant rats. Administration of taftsin induced in these animals a significant increase in reactivity to stimuli of different modalities, the open-field exploratory activity, rate of alimentary conditioning and its modification in emotionally negative situation. Biochemical examinations showed that in rats with high resistance to stress taftsin administration led to a decrease in hypothalamic noradrenaline level and increase in dopamine and serotonin levels. On the contrary, in low-resistant animals taftsin increased the level of noradrenaline and decreased that of dopamine, serotonin, and 5-hydroxyindoleacetic acid. It is suggested that different behavioral effects of taftsin in stress-resistant and nonresistant rats are caused by its different influence on hypothalamic biogenic amines.