Effects of acute and chronic apomorphine on sex behavior and copulation-induced neural activation in the male rat

Abstract

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 matinginduced 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. Fosimmunoreactivity 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 Fosimmunoreactivity 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.

Sexual Dysfunction, Depression and Antidepressants: A Translational Approach

“…This small and short-living facilitatory effect of bupropion was rather unexpected. Apomorphine [41], a mixed dopamine D 2 /D 3 receptor agonist showed a comparable profile in a similar experiment ( ↓: inhibition; ↑: stimulation; 0: no effect; nt: not tested. SSRI: selective serotonergic reuptake inhibitor; SNRI: serotonergic and noradrenergic reuptake inhibitor; NDRI: noradrenergic and dopaminergic reuptake inhibitor; TRI: triple monoaminergic reuptake inhibitor; R: receptor.…”

Mondia whitei (Periplocaceae) prevents and Guibourtia tessmannii (Caesalpiniaceae) facilitates fictive ejaculation in spinal male rats

“…It has been demonstrated that fictive ejaculation can be pharmacologically induced by the systemic injection of dopamine or apomorphine acting at the spinal generator for ejaculation [21,33,34,44] and it has been considered as the main model for the study of the spinal pattern generator of ejaculation [8]. Thus, with no doubt, the effect of the aphrodisiac plants could be systemically evaluated by using the fictive ejaculation model and particular results, highlight the differential effects of aphrodisiac plants.…”

“…Growing evidence shows that dopamine is a neurotransmitter playing a central role in the control of ejaculation [31,32]. Thus, for instance, stimulation of dopaminergic receptors by systemic dopamine [21] or apomorphine [33,34] provokes the expression of ejaculation in spinal male rats. On the other side, systemic administration of antagonists of dopaminergic receptors abolishes the expression of the ejaculatory response in spinal rats [35,36].…”

Neural mechanisms of reproduction in females as a predisposing factor for drug addiction

“…We have provided an overview of mechanisms through which different components of a female’s reproductive experiences can alter dopamine neurotransmission in a way that the system shows a sensitized response to drugs even upon the initial exposure. Our focus has been on reproductive events in females, though it is important to note that there is a rich literature in rats demonstrating that male sexual experience sensitizes the mesolimbic dopamine system [8,9,68,159,168,205] in much the same way as we have described for females.…”