Pulsatile gonadotropin‐releasing hormone (GnRH) secretion was studied in vitro using explants of the retrochiasmatic hypothalamus from prepubertal male and female rats. Leptin caused a dose‐dependent reduction of the GnRH interpulse interval in both sexes. We studied the effects of cocaine‐ and amphetamine‐regulated transcript (CART) since this peptide was shown recently to mediate the anorectic effects of leptin in the hypothalamus. CART caused a reduction of the GnRH interpulse interval. This effect was prevented using an anti‐CART antiserum which could partially overcome leptin stimulatory effects as well. Using hypothalamic explants from Zucker rats homozygous for the leptin receptor mutation ( fa/fa), GnRH pulse frequency was not affected by leptin, while a significant acceleration was caused by the CART‐peptide. In conclusion, leptin involves the hypothalamic CART‐peptide to stimulate the prepubertal GnRH pulse generator in vitro.