Besides the potential direct effects of ginseng/ginsenosides on penile nerve and vascular tissues, ginsenosides may also exert actions on the brain to modulate neurotransmission. Ginsenosides, notably Rb1, Rc, Rg1, and Rg3, facilitate acetylcholine activity [43, 44], are neuroprotective [45-48], and alter neurotransmitter availability [49-52]. The neurotransmitter dopamine plays a central role in sexual behav ior [53, 54], and treatment with dopaminergic drugs has long been shown to facilitate masculine sexual behavior [55, 56]. In the paraventricular nuclei (PVN) and medial preoptic area of the hypothalamus (MPOA), brain areas critical for male sexual behavior , dopamine levels are increased before and during copulation [58, 59]. The microinjection of dopamine receptor antagonists directly into the MPOA decreases libido and impairs copulatory performance [60, 61]. NO may be an important mediator of hypothalamic dopamine release . Treatment with NOS inhibitors decreased hypothalamic dopamine levels  and reduced male mounting activity [64, 65], libido , and penile erection [66, 67]. Although there is no direct evidence to show that ginseng/ginsenosides modulate hypothalamic NO levels, the injection of ginsenoside Rc or Rg3 into the cerebral ventricles inhibits stress-induced hypothalamic activation in mice through a NO-mediated pathway , suggesting that ginsenosides directly induce NO production in the brain. Moreover, oral ginseng treatment was shown to increase striatal dopamine activity  and decrease plasma prolactin levels  in young adult male rats, consistent with a putative role for dopamine in ginseng-induced enhancement of copulatory behaviors.
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