Ruboxistaurin Reduces Cocaine-Stimulated Increases in Extracellular Dopamine by Modifying Dopamine-Autoreceptor Activity

Abstract

Cocaine is a highly abused drug and cocaine addiction affects millions of individuals worldwide. Cocaine blocks normal uptake function at the dopamine transporter (DAT), thus increasing extracellular dopamine. Currently, no chemical therapies are available to treat cocaine abuse. Previous works showed that the selective inhibitors of protein kinase Cβ (PKCβ), enzastaurin and ruboxistaurin, attenuate dopamine overflow and locomotion stimulated by another psychostimulant drug, amphetamine. We now test if ruboxistaurin similarly affects cocaine action. Perfusion of 1 μM ruboxistaurin directly into the core of the nucleus accumbens via retrodialysis reduced cocaine-stimulated increases in dopamine overflow, measured using microdialysis sampling, with simultaneous reductions in locomotor behavior. Because cocaine activity is highly regulated by dopamine autoreceptors, we examined whether ruboxistaurin was acting at the level of the D2-autoreceptor. Perfusion of 5 μM raclopride, a selective D2-like receptor antagonist, before addition of ruboxistaurin abrogated the effect of ruboxistaurin on cocaine-stimulated dopamine overflow and hyperlocomotion. Further, ruboxistaurin was inactive against cocainestimulated locomotor activity in mice with a genetic deletion in D2 receptors as compared to wild type mice. In contrast, blockade or deletion of dopamine D2 receptors did not abolish the attenuating effect of ruboxistaurin on amphetamine-stimulated activities. Therefore, the inhibition of PKCβ reduces dopamine overflow and locomotor activity stimulated by both cocaine and amphetamine, but the mechanism of action differs for each stimulant. These data suggest that inhibition of PKCβ would serve as a target to reduce the abuse of either amphetamine or cocaine.

Presynaptic Gq-coupled receptors drive biphasic dopamine transporter trafficking that modulates dopamine clearance and motor function

“…Previous studies reported that DRD2-stimulated DAT insertion in striatal synaptosomes requires PKCβ activity ( 39 ). To test whether hM3Dq-stimulated DAT insertion was similarly dependent upon PKCβ activity, we pretreated slices with the PKCβ-specific inhibitor ruboxistaurin ( 46 , 47 ) (50 nM, 30 min, 37 °C), prior to activating hM3Dq with CNO. Ruboxistaurin pretreatment completely abolished CNO-stimulated DAT insertion as compared with vehicle-pretreated slices ( Fig.…”

Carbon Nanotube Yarn Microelectrodes Promote High Temporal Measurements of Serotonin Using Fast Scan Cyclic Voltammetry

“…The neurotransmitters that we chose were the catecholamine dopamine, the monoamine serotonin, and the anionic interferants ascorbic acid, and uric acid. Dopamine is an important catecholamine and monoamine neurotransmitter important for understanding the Parkinson's Disease [40], amphetamine abuse [41,42], cocaine abuse [1], and other decision-making capabilities. Serotonin regulates mood and behavior and the depletion of serotonin in the synaptic cleft causes depression [43].…”

“…Neurochemical detection has proven to be important for the understanding and treatment of several diseases, behaviors, and pharmacological drug states. The detection of dopamine is crucial for understanding Parkinson's disease and drug abuse [1], while selective serotonin reuptake inhibitors (SSRIs) are used as treatments for depression [2]. Neurochemical measurements are also important in studying other disease states such as epilepsy [3,4] and obesity [5].…”

Presynaptic Gq-coupled receptors drive biphasic dopamine transporter trafficking that modulates dopamine clearance and motor function

“…Previous studies reported that DRD2-stimulated DAT insertion in striatal synaptosomes requires PKC β activity(40). To test whether hM3Dq-stimulated DAT insertion was similarly dependent upon PKC β activity, we pretreated slices with the PKC β -specific inhibitor ruboxistaurin(47, 48) (50nM, 30 min, 37°C), prior to CNO-stimulated DAT insertion. Ruboxistaurin pretreatment completely abolished CNO-stimulated DAT insertion as compared to vehicle-pretreated slices (Fig.…”