RESUMEN
Methcathinone (MCAT) is a monoamine releaser and parent compound to a new class of designer drugs that includes the synthetic cathinones mephedrone and flephedrone. Using MCAT and a series of para-substituted (or 4-substituted) MCAT analogs, it has been previously shown that expression of abuse-related behavioral effects in rats correlates both with the volume of the para substituent and in vitro neurochemical selectivity to promote monoamine release via the dopamine (DA) versus serotonin (5-HT) transporters in rat brain synaptosomes. The present study used in vivo microdialysis to determine the relationship between these previous measures and the in vivo neurochemical selectivity of these compounds to alter nucleus accumbens (NAc) DA and 5-HT levels. Male Sprague-Dawley rats were implanted with bilateral guide cannulae targeting the NAc. MCAT and five para-substituted analogs (4-F, 4-Cl, 4-Br, 4-CH3, and 4-OCH3) produced dose- and time-dependent increases in NAc DA and/or 5-HT levels. Selectivity was determined as the dose required to increase peak 5-HT levels by 250% divided by the dose required to increase peak DA levels by 250%. This measure of in vivo neurochemical selectivity varied across compounds and correlated with 1) in vivo expression of abuse-related behavioral effects (r = 0.89, P = 0.02); 2) in vitro selectivity to promote monoamine release via DA and 5-HT transporters (r = 0.95, P < 0.01); and 3) molecular volume of the para substituent (r = -0.85, P = 0.03). These results support a relationship between these molecular, neurochemical, and behavioral measures and support a role for molecular structure as a determinant of abuse-related neurochemical and behavioral effects of MCAT analogs.
Asunto(s)
Drogas de Diseño/toxicidad , Dopamina/metabolismo , Núcleo Accumbens/metabolismo , Propiofenonas/toxicidad , Serotonina/metabolismo , Trastornos Relacionados con Sustancias/metabolismo , Anfetamina/farmacología , Animales , Conducta Animal/efectos de los fármacos , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/metabolismo , Inhibidores de Captación de Dopamina/farmacología , Relación Dosis-Respuesta a Droga , Fenfluramina/farmacología , Masculino , Metanfetamina/análogos & derivados , Metanfetamina/toxicidad , Microdiálisis , Núcleo Accumbens/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Proteínas de Transporte de Serotonina en la Membrana Plasmática/metabolismo , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Trastornos Relacionados con Sustancias/psicología , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismoRESUMEN
Phendimetrazine (PDM) is a clinically available anorectic and a candidate pharmacotherapy for cocaine addiction. PDM has been hypothesized to function as a prodrug that requires metabolism to the amphetamine-like monoamine transporter substrate phenmetrazine (PM) to produce its pharmacological effects; however, whether PDM functions as an inactive prodrug or has pharmacological activity on its own remains unclear. The study aim was to determine PDM pharmacological mechanisms using electrophysiological, neurochemical, and behavioral procedures. PDM blocked the endogenous basal hDAT (human dopamine transporter) current in voltage-clamped (-60 mV) oocytes consistent with a DAT inhibitor profile, whereas its metabolite PM induced an inward hDAT current consistent with a DAT substrate profile. PDM also attenuated the PM-induced inward current during co-application, providing further evidence that PDM functions as a DAT inhibitor. PDM increased nucleus accumbens dopamine levels and facilitated electrical brain stimulation reinforcement within 10 min in rats, providing in vivo evidence supporting PDM pharmacological activity. These results demonstrate that PDM functions as a DAT inhibitor that may also interact with the pharmacological effects of its metabolite PM. Overall, these results suggest a novel mechanism for PDM therapeutic effects via initial PDM DAT inhibition followed by PM DAT substrate-induced dopamine release.