BEHAVIORAL AND NEUROBIOLOGICAL CONSEQUENCES OF SOCIAL SUBJUGATION DURING PUBERTY IN GOLDEN-HAMSTERS

In golden hamsters, offensive aggression is facilitated by vasopressin and inhibited by serotonin. We tested whether these neurotransmitter systems respond to modifications resulting from the stress of threat a nd attack (i.e., social subjugation) during puberty. Male golden hamst ers were weaned at postnatal day 25 (P25), exposed daily to aggressive adults from P28 to P42, and tested for offensive aggression as young adults (P45). The results showed a context-dependent alteration in agg ressive behavior. Subjugated animals were more likely to attack younge r and weaker intruders than nonsubjugated controls. Conversely, subjug ated animals were less likely to attack animals of similar size and ag e. After testing, the animals were killed, and their brains were colle cted to determine whether these behavioral changes are underlined by c hanges in the vasopressin and serotonin systems. Social subjugation re sulted in a 50% decrease in vasopressin levels within the anterior hyp othalamus, a site involved in the regulation of aggression. Furthermor e, whereas the density of vasopressin-immunoreactive fibers within the area was not significantly altered in subjugated animals, the number of serotonin-immunoreactive varicosities within the anterior hypothala mus and lateral septum was 20% higher in subjugated animals than in th eir controls. These results establish puberty as a developmental perio d sensitive to environmental stressors. Furthermore, the results show that changes in the vasopressin and serotonin systems can correlate wi th behavioral alterations, supporting the role of these two neurotrans mitters in the regulation of aggression.