Pubertal stress accelerates copulation in adult male rats: Mitigating effects of a high-calorie diet in adulthood

The pubertal phase involves significant brain reorganization, where external stressors and diet can profoundly influence long-term behavioral outcomes. In this study, we investigated the interaction between acute pubertal stress (via immune challenge) and a hypercaloric diet in adulthood on the copulatory sexual behavior of male Wistar rats. At postnatal day (PND) 35, pubertal males received a single injection of lipopolysaccharide (LPS, 1.5 mg/kg i.p.) or saline. All subjects were fed standard rat chow until postnatal week 14, during which copulatory sexual behavior was assessed from weeks 11 to 14. Then, from weeks 15 to 18, half of the animals in each group were switched to a hypercaloric cafeteria-type diet and the other half continued on standard chow, with sexual behavior of all males re-assessed during weeks 19 to 22 and under standard diet. Our results indicated that treatment with LPS during puberty accelerated copulation in adulthood, characterized by fewer mounts and intromissions per series, shorter latency to ejaculation and higher intromission ratio. Cafeteria diet alone increased mount and intromission frequency, but had no effect on ejaculations. Only intromission were affected by an interaction of treatment and diet. These findings show that LPS-induced immune stress during puberty acts as an early-life stressor with enduring consequences on copulatory timing in males, while a subchronic hypercaloric diet in adulthood may mitigate some of these effects.