MK-212

MK-212, also known as 6-chloro-2-pyrazine, is a receptor agonist">receptor (biochemistry)">receptor agonist of the arylpiperazine family. It is specifically described as a non-selective serotonin 5-HT₂ receptor agonist or as a "relatively selective serotonin 5-HT_2C receptor full agonist. The drug promotes the secretion of serum prolactin and cortisol in humans.

Use and effects

MK-212 did not produce hallucinogenic effects in humans at doses of up to 40mg orally. However, in other research, it occasionally produced LSD-like effects in alcoholic patients at a dose of 20mg. In addition, subsequent studies found that MK-212 at 20mg significantly increased ratings of feeling high and feeling strange.

MK-212 is an agonist of the serotonin 5-HT₂ receptors, including the serotonin 5-HT_2C, 5-HT_2B, and 5-HT_2A receptors, in that order of potency. It is a full agonist of the serotonin 5-HT_2C receptor, a moderate-efficacy partial agonist of the serotonin 5-HT_2B receptor, and a partial to full agonist of the serotonin 5-HT_2A receptor. The drug shows similar potency in activating the serotonin 5-HT_2C and 5-HT_2B receptors and around 10- to 30-fold lower relative potency in activating the serotonin 5-HT_2A receptor. It also shows low affinity for the serotonin 5-HT_1A and 5-HT_1B receptors. THe comprehensive receptor interactions of MK-212 have been studied.
In a 1977 study by Clineschidt and colleagues, they dosed mice with varying concentrations of MK-212, and observed its effects.
The result correlated very well to binding of indolealkylamine receptors, such as the serotonin and tryptamine receptors, which shows four characteristics. Namely, increased frequency of muscle twitching, increased twitching of the head, "an increase in the strength of the crossed extensor reflex in the acutely spinalized rat", and the cause of complex motor syndrome.