S. Kollackwalker et Sw. Newman, MATING-INDUCED EXPRESSION OF C-FOS IN THE MALE SYRIAN-HAMSTER BRAIN -ROLE OF EXPERIENCE, PHEROMONES, AND EJACULATIONS, Journal of neurobiology, 32(5), 1997, pp. 481-501
This study was designed to investigate the effects of pheromonal cues
and specific behaviors within the male copulatory sequence on c-fos ex
pression in the medial nucleus of the amygdala (Me), the bed nucleus o
f the stria terminalis (BNST), and the medial preoptic area (MPOA) of
the Syrian hamster brain. Sexually experienced male hamsters were plac
ed into clean testing arenas and were either: 1) left alone as handled
controls; 2) exposed to female hamster vaginal secretion (FHVS) on co
tton swabs; or mated to various end points of copulation with a sexual
ly receptive female: 3) five intromissions, 4) one ejaculation, 5) fiv
e ejaculations, or 6) long intromissions. A seventh group of sexually
naive control males 7) was left alone in the arena. The brains of thes
e males were compared to those of the sexually experienced controls to
determine whether exposure to cues associated with prior sexual exper
ience could alter c-fos expression. In males exposed only to FHVS, Fos
immunoreactivity (Fos-ir) increased within the posterodorsal Me, the
anterodorsal part of the posteromedial BNST, and the magnocellular med
ial preoptic nucleus (MPNmag). Following one ejaculation, Fos-ir incre
ased within the caudal posterodorsal Me, the dorsolateral MPOA, and th
e paraventricular nucleus of the hypothalamus. After multiple ejaculat
ions, additional labeling was observed within the posteroventral part
of the posteromedial BNST, the medial preoptic nucleus (MPN), the cent
ral tegmental field, and in cell clusters of the caudal posterodorsal
Me and rostral posteromedial BNST. Fos-ir also increased within the po
sterodorsal Me, MPN, and MPNmag in sexually experienced control males
exposed to the empty test chamber compared to sexually naive males exp
osed to an identical chamber. These results demonstrate that the matin
g-induced pattern of neuronal activation in sexually experienced males
is dependent upon multiple factors, including prior sexual experience
in the testing environment, investigation of FHVS, and the number of
ejaculations achieved. (C) 1997 John Wiley & Sons, Inc.