Effects of Serotonin 1A or 1B Receptor Agonists on Social Aggression in Male and Female Syrian Hamsters

Numerous studies have demonstrated that activation of serotonin 5-HT 1A or 5-HT 1B receptor decreases aggression in male mammals. To determine whether female mammals also show decreased aggression in response to 5-HT 1A or 5-HT 1B activation, we assessed the effects of the serotonin receptor agonists 8-OH-DPAT (5-HT 1A) and CGS-12066A (5-HT 1B) on aggression in female Syrian hamsters. Female Syrian hamsters were tested for interfemale aggression 2 days before and 15 min after receiving intracerebroventricular infusions of 8-OH-DPAT (5, 10, 20 μg) or CGS-12066A (5, 10, 20 μg). Neither drug affected aggression as measured by the latency and frequency of attacks or uprights, although the highest dose of 8-OH-DPAT increased general activity. For male hamsters, intraventricular infusions of 10 μg of 8-OH-DPAT essentially eliminated aggression, whereas 5 μg of 8-OH-DPAT or 20 μg of CGS-12066A were without effect. Systemic treatment with 8-OH-DPAT (1 mg/kg body weight) did reduce aggression in females, although there was an attendant increase in symptoms of nonspecific serotonergic activity. There were no behavioral effects of systemic CGS-12066A (4 mg/kg body weight) on female hamsters. These results indicate that there may be sex differences in the neurochemical regulation of aggression and point to a need for more studies directed at this issue.