Methcathinone and methylone were threefold less potent than MA or MDMA at inhibiting [3H]5-HT uptake into human platelets, with IC50's of 31.4 ± 7.3 uM and 5.8 ± 0.7 uM, respectively. In C6 glial cells stably expressing the rat dopamine transporter, methcathinone and methylone were similar in potency to MA and MDMA, with IC50's for [3H]DA uptake of 0.36 ± 0.06 uM and 0.82 ± 0.17 uM, respectively. Methcathinone and methylone were also similar in potency to MA and MDMA in C6 cells expressing the human norepinephrine transporter, with IC50's for [3H]NE accumulation of 0.51 ± 0.10 uM and 1.2 ± 0.1 uM, respectively.
The benzylic ketone moiety of methcathinone and methylone had a large (tenfold) negative impact on the abilities of these drugs to inhibit the vesicular monoamine transporter (VMAT2) compared to MA and MDMA.
So, we see that the simple addition of a beta-ketone moiety to a PEA which normally had affinity for the VMAT2 drops the new compound's ability to interact with that receptor by 1000%!
For those unaware of the rather large implications of this:
VMAT2 is essential in the presynaptic neuron's ability to facilitate the release of neurotransmitters into the synaptic cleft.
Therefore it seems these compounds, methcathinone and methylone [being literally 10x less efficient at interfacing with this receptor when compared to their monoamine releasing homologues methamphetamine and MDMA] are primarily re-uptake inhibitors, as they cannot bind to the VMAT2 with sufficient force as to facilitate release. Furthermore, these findings can almost certainly be applied to all the beta-keto compounds.
Got a knowledge bomb or two up my sleeve. Since we can assume brephedrone doesn't activate VMAT2, and therefore is a simple reuptake inhibitor, our conclusion regarding it's toxicity becomes increasingly clear. Drugs which only reuptake monoamines are generally much more benign as far as neurotoxicity. Even during simultaneous and strong serotonin release via MDAI, co-administration of a simple DARI resulted in *no* neurotoxicity. And THAT's straight from Nichols.