Friday, July 15, 2011

Gingko Biloba, Your Dopaminergic Brain Viagra. Plant Extract Stimulates Sexual Arousal via the Paraventricular Nucleus and the Mesolimbic System.

Image 1: Gingko biloba
trees are one of a kind, with
no close living relatives
(image Schwabe Pharm.)
I bet you got one of those Viagra spam mails, today, as well, didn't you? Well, although I assume you would not need the small blue pills, anyway, you may be interest to read that researchers from the People's Republic of China may have found a viable Viagra alternative in a longstanding (pun intended ;-) ingredient of Traditional Chinese (and meanwhile also Western) Medicine: Gingko biloba.

In order to elucidate the underlying mechanisms of previously (Yeh. 2010) observed beneficial effects of Ginkgo biloba extract on noncontact erections in male rats, Yeh et al. (Yeh. 2011) recorded both copulation, as well as non-contact erections in a group of 20 male Long-Evans (telling name, isn't it?) rats, which had been randomly assigned to a treatment (50mg/kg body weight Gingko biloba extract [EGb 761 from Schwabe Pharmaceuticals], human equivalent 8mg/kg ~ 640mg for an 80kg man) or a control group. 14 days after initiation of treatment, there was "a significant increase in the number of NCEs [non contact erections]" in the 10 rats of the treatment group. Furthermore,
[...] the expression of catecholaminergic neurons in the PVN [paraventricular nucleus] and the VTA [ventral tegmental area] was seen [to be significantly increased ...] and tissue levels of dopamine and 3,4-dihydroxyphenylacetic acid in the NAc [nucleus accubens] were also markedly increased in the EGb 761-treated animals. However, the norepinephrine tissue levels in the PVN and the NAc in the EGb 761-treated group were not significantly different from those in the controls.
In other words, the increased number of catecholaminergic neurons did not, as one might have expected, increase the total amount of the stress-related neurotransmitter /hormone norepinephrine. In agreement with previous work by Mas et al., 1990; Pfaus et al., 1990; Pleim et al., 1990;Wenkstern et al., 1993; Tsai et al., 2006, it's dopaminergenic effects in the nuccleus accubens (dopamine levels in the increased by 66%), on the other hand, had profound effects on their sexual behavior (cf. figure 1).
Figure 1: Effect of Gingko biloba extract @ 50mg/kg on non-contact erection frequency in male Long-Evans rats before and after 14 day treatment (data adapted from Yeh. 2011)
In view of the effect, that the scientist do not want to "exclude that EGb 761 treatment may also influence dopaminergic activity in other brain areas", these results may be of interest even to those among you, who do not have any trouble "getting it up".
Note: The mechanism by which Gingko biloba increases sexual desire is different from the one of PDE-5 inhibitors such as avanafil, lodenafil, mirodenafil, sildenafil citrate, tadalafil and all the other "-afils". While the systemic effect on nitric oxide induced vasolidation of Viagra and Co. will help with erection quality and quantity, Gingko biloba probably won't help if blood flow restriction in your most valuable part is an issue. The different mechanisms of action, on the other hand, would suggest the two would make an interesting stack. And in fact back in 2010 Kim et al. found that "GBE [Gingko biloba extract] could increase the relaxant potency of mirodenafil even at a minimally effective dose" (Kim. 2010).
With dopamine playing an important role in behavior and cognition, voluntary movement, motivation, punishment and reward, inhibition of prolactin production (juicers did you read that?), sleep, mood, attention, working memory, and learning, the implications of this finding reach beyond sexual function alone. Even in the etiology of the dubious central fatique syndrome, every second visitor of one of the major internet health bulletin boards claims to experience, these days, may involve dopamine or rather a lack thereof (Caldizán Uzón. 2008). That being said, the group of patients who benefit from one of the readily available over-the-counter Gingko biloba supplements may soon expand from best agers, who are concerned about cognitive decline to (pre-)andropausal men who want to regain their interest in the fairer sex and, eventually, everyone who feels he/she would benefit from some additional dopaminergic drive.