title: An enriched rearing environment calms adult male rat sexual activity: implication for distinct serotonergic and hormonal responses to females.
abstract: Early life events induce alterations in neural function in adulthood. Although rearing in an enriched environment (EE) has a great impact on behavioral development, the effects of enriched rearing on sociosexual behavior remain unclear. In this study, we investigated the effects of rearing in an EE on male copulatory behavior and its underlying neurobiological mechanisms in Wistar-Imamichi rats. Three-week-old, recently weaned rats were continuously subjected to a standard environment (SE) or an EE comprised of a large cage with several objects, such as toys, tunnels, ladders, and a running wheel. After 6 weeks, rats reared in an EE (EE rats) showed decreased sexual activity compared with rats reared in a SE (SE rats). This included a lower number of ejaculations and longer latencies in three consecutive copulatory tests. In addition, EE rats showed decreased emotional responsiveness and less locomotor behavior in an open field. In a runway test, on the other hand, sexual motivation toward receptive females in EE males was comparable to that of SE males. Furthermore, following exposure to a female, increases in serotonin levels in the nucleus accumbens and the striatum were significantly suppressed in EE males, whereas dopaminergic responses were similar between the groups. Female-exposure-induced increases in the levels of plasma corticosterone and testosterone were also suppressed in EE rats compared to SE rats. These data suggest that rearing in an EE decreases male copulatory behavior, and serotonin and hormonal regulating systems may regulate the differences in sociosexual interactions that result from distinct rearing environments.
authors: Department of Physiology, Nippon Medical School, Tokyo, Japan ; Department of Judo Neurophysiotherapy, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
authors: Susumu
authors: S
authors: Urakawa
authors: Department of Systems Neuroscience, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan.
authors: Dai
authors: D
authors: Mitsushima
authors: Department of Environmental Veterinary Sciences, Hokkaido University, Hokkaido, Japan ; Laboratory of Veterinary Ethology, The University of Tokyo, Tokyo, Japan.
authors: Michito
authors: M
authors: Shimozuru
authors: Department of Physiology, Nippon Medical School, Tokyo, Japan.
authors: Yasuo
authors: Y
authors: Sakuma
authors: Department of Physiology, Nippon Medical School, Tokyo, Japan ; Department of Animal Sciences, Teikyo University of Science, Tokyo, Japan.
authors: Yasuhiko
authors: Y
authors: Kondo
mesh_terms: D000818:Animals; D003307:Copulation / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D008124:Locomotion / Q000502:physiology; D008297:Male; D052586:Mating Preference, Animal / Q000502:physiology*; D009714:Nucleus Accumbens / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
chemical_list: D012701:Serotonin; D013739:Testosterone; D004298:Dopamine