Effects of neonatal clomipramine treatment on locomotor activity, anxiety-related behavior and serotonin turnover in Syrian hamsters.

Day-night differences in locomotor and anxiety-related behavior and brain serotonin metabolism were examined in adult Syrian hamsters that received clomipramine (15 mg/kg) or vehicle from day 8 to day 21 of life. Locomotor activity was significantly greater at the beginning of scotophase (20.00 h) than at noon (12.00 h) and it was highest in hamsters treated with clomipramine at both examined times. Significant day-night differences in anxiety-related behavior, as measured in a plus-maze paradigm, were found in saline-treated hamsters only, with higher values at night. Clomipramine-treated hamsters exhibited augmented 5-hydroxyindoleacetic acid/serotonin ratio in hypothalamus and midbrain raphe, while serotonin content decreased in frontal cortex and hypothalamic areas. The results indicate that neonatal clomipramine treatment produces a long-lasting change in locomotion and anxiety-related behavior, as well as reduces brain serotonin content in hamsters.