Newsgroups: alt.drugs From: William E. White Subject: Re: Yohimbe Date: Mon, 3 Oct 1994 00:18:34 GMT Yohimbine, the active constituent in yohimbe bark (there may be others, since yohimbine alone does not seem to produce the same effects as the bark extract), is an alpha-2 adrenergic antagonist. It is not, to my knowledge, an MAOI (if someone knows differently, please inform me). [Erowid Note: According to Quinton RM. B J Pharmacology 1963 21:51-66, yohimbine is in fact a very weak MAOI, but this may not be clinically relevant. Yohimbine has been shown to be potentially dangerous in combination with other drugs such as SSRIs and amphetamines, which is similar to contraindications for MAOIs, but the problems may not be related to yohimbine's MAO-Inhibition. Also, Yohimbe products should NOT be taken with other MAOIs.] The alpha-2 receptor is an autoreceptor (presynaptic, I think) which acts as a kind of "thermostat" to adrenergic activity. That is, some of the noradrenaline released by a neuron goes back to the alpha-2 autoreceptor, which then REDUCES the amount of noradrenaline secreted. This is similar to a thermostat, which registers the temperature and reduces the amount of heat produced when the air warms up. By blocking the alpha-2 autoreceptor, yohimbine increases the amount of adrenergic activity. Additionally, it does so in a different way than a simple agonist (which would universally activate receptors, rather than amplifying existing noradrenergic activity) would do. Yohimbine is used medically to treat impotence, as increased adrenergic activity seems to help. I think "Yocon" is the brand name. Yohimbe / yohimbine are contraindicated in people with high blood pressure, heart problems, anxiety, and panic attacks, all of which can be made worse with adrenergic activity. It should not be taken with any stimulant. Avoid MAOIs with yohimbine. >understanding, MAO inhibitors keep certain receptor points in your brain >open, making other substances *much* more potent. MAOIs prevent monoamine oxidase, an enzyme (actually two enzymes) from degrading certain substances. For example, orally ingested DMT is normally broken down by MAO before it ever reaches the brain (if you smoke it, some will make it there). By inhibiting MAO, the DMT stays around until it is degraded by other (much slower) pathways. The troubles with MAOIs are twofold: First, some chemicals are degraded by MAOI, but when undegraded can be dangerous; an example of this is tyramine, an amino acid present in cheese, wine, etc., which is an indirectly acting sympathomimetic (like amphetamine). Normally no tyramine makes it to your brain when you eat cheese, but if you are taking a MAOI, you can end up in a hypertensive crisis. Second, and more insidiously, sometimes there is an enzyme pathway from a harmless substance to a more harmful one, which is "uncovered" when the (more active) MAO pathway is inhibited.