GZ-793A, a lobelane analog, interacts with the vesicular monoamine transporter-2 to inhibit the effect of methamphetamine

(R)-3-[2,6-cis-Di(4-methoxyphenethyl)piperidin-1-yl]propane-1,2-diol (GZ-793A) inhibits methamphetamine-evoked dopamine release from striatal slices and methamphetamine self-administration in rats. GZ-793A potently and selectively inhibits dopamine uptake at the vesicular monoamine transporter-2 (VMAT2). This study determined GZ-793A's ability to evoke [³H] dopamine release and inhibit methamphetamine-evoked [³H]dopamine release from isolated striatal synaptic vesicles. Results show GZ-793A concentration-dependent [³H]dopamine release; nonlinear regression revealed a two-site model of interaction with VMAT2 (High- and Low-EC ₅₀ = 15.5 nM and 29.3 μM, respectively). Tetrabenazine and reserpine completely inhibited GZ-793A-evoked [³H]dopamine release, however, only at the High-affinity site. Low concentrations of GZ-793A that interact with the extravesicular dopamine uptake site and the High-affinity intravesicular DA release site also inhibited methamphetamine-evoked [ ³H]dopamine release from synaptic vesicles. A rightward shift in the methamphetamine concentration-response was evident with increasing concentrations of GZ-793A, and the Schild regression slope was 0.49 ± 0.08, consistent with surmountable allosteric inhibition. These results support a hypothetical model of GZ-793A interaction at more than one site on the VMAT2 protein, which explains its potent inhibition of dopamine uptake, dopamine release via a High-affinity tetrabenazine- and reserpine-sensitive site, dopamine release via a Low-affinity tetrabenazine- and reserpine-insensitive site, and a low-affinity interaction with the dihydrotetrabenazine binding site on VMAT2. GZ-793A inhibition of the effects of methamphetamine supports its potential as a therapeutic agent for the treatment of methamphetamine abuse. GZ-793A inhibits methamphetamine-evoked dopamine release from synaptic vesicles through a surmountable allosteric mechanism and interacts with several sites on the vesicular monoamine transporter-2 (VMAT2), including high- and-low affinity intravesicular dopamine release sites, high-affinity extravesicular dopamine uptake sites and low-affinity extravesicular dihydrotetrabenazine binding sites. VMAT2 interactions likely underlie the ability of GZ-793A to attenuate the neurochemical and behavioral effects of methamphetamine. GZ-793A inhibits methamphetamine-evoked dopamine release from synaptic vesicles through a surmountable allosteric mechanism and interacts with several sites on the vesicular monoamine transporter-2 (VMAT2), including high- and-low affinity intravesicular dopamine release sites, high-affinity extravesicular dopamine uptake sites and low-affinity extravesicular dihydrotetrabenazine binding sites. VMAT2 interactions likely underlie the ability of GZ-793A to attenuate the neurochemical and behavioral effects of methamphetamine.