Sexual behavior of the obese male Zucker rat.

Obese male Zucker rats displayed inadequate sexual behavior at four months placed with ovariectomized lean females pretreated with estrogen and progesterone. Only one out of seven obese males ejaculated during the test sessions. Diet-restricting the obese males at five months of age did not improve their sexual behavior when tested at six months of age. At ten months of age none of the obese males ejaculated during the test sessions. Lean littermates ejaculated during the sessions at all ages tested. Obese males which do ejaculate are capable of inducing pseudopregnancy in intact lean females. These findings suggest that inadequate sexual behavior is one factor contributing to the reduced reproductive capacity of obese male Zucker rats.