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 s erotonin metabolism were examined in adult Syrian hamsters that received cl omipramine (15 mg/kg) or vehicle from day 8 to day 21 of life. Locomotor ac tivity was significantly greater at the beginning of scotophase (20.00 h) t han at noon (12.00 h) and it was highest in hamsters treated with clomipram ine at both examined times. Significant day-night differences in anxiety-re lated behavior, as measured in a plus-maze paradigm, were found in saline-t reated hamsters only, with higher values at night. Clomipramine-treated ham sters exhibited augmented 5-hydroxyindoleacetic acid/serotonin ratio in hyp othalamus and midbrain raphe, while serotonin content decreased in frontal cortex and hypothalamic areas. The results indicate that neonatal clomipram ine treatment produces a long-lasting change in locomotion and anxiety-rela ted behavior, as well as reduces brain serotonin content in hamsters.