Effects of acute and chronic apomorphine on sex behavior and copulation-induced neural activation in the male rat.
Apomorphine is a non-selective dopaminergic receptor agonist. Because of its pro-erectile effects, apomorphine is clinically used for treatment of erectile dysfunction. We investigated the effects of subcutaneous apomorphine administration (0.4 mg/kg rat) on sexual behavior and mating-induced Fos-expression following acute (day 1) or chronic apomorphine treatment (days 8 and 15) in sexually experienced male rats. Consistent facilitatory effects of apomorphine were observed in the reduced numbers of mounts and intromissions over time and an increased ejaculation frequency on day 1. The first post-ejaculatory interval, however, was lengthened, while other behavioral parameters were unaffected. Fos-immunoreactivity induced by acute apomorphine administration (barrel cortex, paraventricular hypothalamic nucleus, central amygdala and locus coeruleus) was strongly reduced after chronic administration. After mating, induction of Fos-immunoreactivity was observed in well-known areas like medial preoptic nucleus and the posterodorsal medial amygdaloid area. Apomorphine, however, reduced mating-induced Fos-immunoreactivity in the nucleus accumbens shell and prevented its occurrence in its core area. This remarkable apomorphine effect was not observed in any other brain area. We conclude that the behavioral (pro-erectile) effects of apomorphine are consistent over time, and that the diminished accumbens-Fos-immunoreactivity and the elongated post-ejaculatory interval may reflect a decreased response to remote cues from the estrus female.
Olivier
Jocelien D A
JD
Department of Anatomy, UMC St Radboud, University of Nijmegen, The Netherlands.
de Jong
Trynke R
TR
Jos Dederen
P
P
van Oorschot
Ruud
R
Heeren
Dick
D
Pattij
Tommy
T
Waldinger
Marcel D
MD
Coolen
Lique M
LM
Cools
Alexander R
AR
Olivier
Berend
B
Veening
Jan G
JG
D000818:Animals; D001058:Apomorphine / Q000008:administration & dosage*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D003307:Copulation / Q000502:physiology; D018491:Dopamine Agonists / Q000008:administration & dosage*; D005260:Female; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012726:Sexual Behavior, Animal / Q000187:drug effects*