title: Winter day lengths counteract stimulatory effects of apomorphine and yohimbine on sexual behavior of male Syrian hamsters.
abstract: Yohimbine and apomorphine selectively act on noradrenergic and dopaminergic neural substrates to augment male sexual behavior (MSB) in several rodent species. The present study assessed whether these drugs can overcome the suppressive effects of short winter-like day lengths on MSB. Yohimbine treatments that markedly increase copulatory behavior of male hamsters in long days were completely ineffective in facilitating MSB when injected after gonadal regression induced by 16 wks of short day lengths and after complete gonadal recrudescence after 32 wks of short days; apomorphine was similarly ineffective. The brain circuit that mediates MSB either may be less responsive to yohimbine and apomorphine in short than long days, or these drugs may not produce equivalent neurotransmitter changes in the two day lengths. After 32 wks of short-day treatment, all males had undergone testicular recrudescence and successfully ejaculated on initial tests with sexually receptive females after a hiatus of at least 4 mo during which they were denied mating opportunities. This suggests that overwintering males in the field are in a state of reproductive readiness at the outset of spring conditions favorable for survival of offspring.
authors: Department of Psychology, University of California-Berkeley, Berkeley, California 94720, USA. piekarski@berkeley.edu
authors: David J
authors: DJ
authors: Piekarski
authors: Stephan G
authors: SG
authors: Jarjisian
authors: Irving
authors: I
authors: Zucker
mesh_terms: D058669:Adrenergic alpha-2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D006224:Cricetinae; D018491:Dopamine Agonists / Q000494:pharmacology; D004542:Ejaculation / Q000187:drug effects / Q000502:physiology; D005260:Female; D008297:Male; D008647:Mesocricetus; D009929:Organ Size / Q000187:drug effects; D017440:Photoperiod; D012621:Seasons; D012726:Sexual Behavior, Animal / Q000187:drug effects* / Q000502:physiology*; D013737:Testis / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology*
chemical_list: D058669:Adrenergic alpha-2 Receptor Antagonists; D018491:Dopamine Agonists; D015016:Yohimbine; D001058:Apomorphine