Effect of neonatal β-endorphin imprinting on sexual behavior and brain serotonin level in adult rats

Abstract A single dose (3 μg) β-endorphin was administered to newborn female and male rats (hormonal imprinting). In adult age (at 5 months) sexual behavior, steroid hormone binding capacity and brain serotonin content was studied. Females' sexual activity (lordosis quotient) significantly decreased and more animals protested against mounting (ratio of kicking and crying 21/24 vs. 8/24; p