Abstract: Observations were made on the changes of behavior in rats such as free activity in the open field, muricide and shock-induced fighting behaviorafter social isolation for 10-12 weeks. Furthermore, the changes of monoa-mine neurotransmitters contents in the brain of the rat were determined and the effect of d-amphetamine and reserpine on shock-induced fighting beha-vior was observed. It was found that there was no obvious influence on freeactivity in the open field and muricide after social isolation. But the shock-induced fighting behavior increased significantly. No significant changes weredetected on monoamine neurotransmitters contents in the brain of sociallyisolated rats. After shock-induced fighting, the DA contents decreased bothin the brain of isolated rats and gregarious rats. NE contents increasedin the telencephalon of gregarious rats, and the 5-HIAA contents in thebrain stem decreased. But no such changes were detected in the brain ofisolated rats. Shock-induced fighting behavior lessened ter reserpine injection upon isolated rats. The probable explanations of the above-men- tioned phenomena are discussed.

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