Dopamine-oxytocin interactions in penile erection.
Dopamine and oxytocin have established roles in the central regulation of penile erection in rats; however, the neural circuitries involved in a specific erectile context and the interaction between dopamine and oxytocin mechanisms remain to be elucidated. The medial preoptic area (MPOA), supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus may serve as candidate sites because they contain oxytocin cells, receive dopaminergic inputs and have been implicated in mediating masculine sexual behavior. Double immunofluorescence revealed that substantial numbers of oxytocin cells in the MPOA, SON and PVN possess dopamine D(2), D(3) and D(4) receptors. In anaesthetized rats, using intracavernous pressure as a physiological indicator of erection, blockade of lumbosacral oxytocin receptors (UK, 427843) reduced erectile responses to a nonselective dopamine agonist (apomorphine), suggesting that dopamine recruits a paraventriculospinal oxytocin pathway. In conscious males in the absence of a female, penile erection elicited by a D(2)/D(3) (Quinelorane) but not D(4) (PD168077) agonist was associated with activation of medial parvocellular PVN oxytocin cells. In another experiment where males were given full access to a receptive female, a D(4) (L-745870) but not D(2) or D(3) antagonist (L-741626; nafadotride) inhibited penile erection (intromission), and this was correlated with SON magnocellular oxytocin neuron activation. Together, the data suggest dopamine's effects on hypothalamic oxytocin cells during penile erection are context-specific. Dopamine may act via different parvocellular and magnocellular oxytocin subpopulations to elicit erectile responses, depending upon whether intromission is performed. This study demonstrates the potential existence of interaction between central dopamine and oxytocin pathways during penile erection, with the SON and PVN serving as integrative sites.
School of Biomedical Sciences, University of Edinburgh, Edinburgh, UK. tab3b@clinmed.gla.ac.uk
T A
TA
Baskerville
J
J
Allard
C
C
Wayman
A J
AJ
Douglas
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006727:Hormone Antagonists / Q000494:pharmacology; D007276:Injections, Intraventricular / Q000379:methods; D008297:Male; D010121:Oxytocin / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D010410:Penile Erection / Q000187:drug effects / Q000523:psychology*; D011301:Preoptic Area / Q000187:drug effects / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011954:Receptors, Dopamine / Q000378:metabolism; D018045:Receptors, Oxytocin / Q000037:antagonists & inhibitors; D012726:Sexual Behavior, Animal / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism; D018709:Statistics, Nonparametric
D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D006727:Hormone Antagonists; D016760:Proto-Oncogene Proteins c-fos; D011954:Receptors, Dopamine; D018045:Receptors, Oxytocin; D010121:Oxytocin; D001058:Apomorphine; D004298:Dopamine