Browsing by Subject "Dopamine--Receptors"
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Item Dopamine and ethanol induced trafficking of viral mediated eGFP tagged dopamine D1 receptors in parasagittal explants(2005) Diaz, Laurea Marie; Morrisett, Richard A.The mesolimbic pathway has been implicated in the rewarding effects of drugs of abuse, and an important component of this pathway is the D1 dopamine receptor (D1DR). D1DRs desensitize upon agonist stimulation by several mechanisms, including a process involving receptor clustering and internalization. This process removes postsynaptic D1DRs and may be a neuroadaptive mechanism associated with addiction to drugs of abuse, including ethanol. We measured localization of D1DRs in viable nucleus accumbens (NAcc) neurons from parasagittal explants. A sindbis RNA virus was used to mediate the expression of D1DRs containing an enhanced green fluorescent protein (eGFP) tag in these explants. The effects of dopamine and ethanol on D1DR localization were measured by changes in fluorescence intensity using two-photon laser scanning microscopy. Two-dimensional images from z-stacks of virally infected neurons displayed stable and homogenous fluorescence throughout the neuronal soma and processes. Dopamine (100 uM, 30 min) significantly enhanced the greatest increase of maximum fluorescence intensity in distinct regions of interest (ROIs) by approximately 40% compared to control neurons in the absence of dopamine. Ethanol pretreatment significantly enhanced dopamine-induced clustering. Neurons exposed to dopamine (50 uM, 30 min) displayed receptor clustering only when pretreated with ethanol. Ethanol (50 and 100 mM, 30 min.) pretreatment followed by dopamine (50 uM, 30 min.) enhanced the greatest increase of maximum fluorescence intensity by 44±3 and 108±9%, respectively, while dopamine (50 uM, 30 min) in the absence of ethanol pretreatment showed no clustering with peak increases in maximum fluorescence intensity of only 3±2%. Ethanol (50 and 100 mM, 60 min) alone enhance the greatest increase of maximum fluorescence intensity by about 60% for both concentrations. Receptor clustering induced by dopamine, ethanol pretreatment of dopamine, or ethanol alone was partially blocked by the D1DR antagonist SCH 23390 (20 uM). These findings show that both dopamine and ethanol alter D1DR localization in NAcc neurons and suggest that a physical restructuring of D1DRs in this region may be involved in neuroadaptive mechanisms of ethanol actionItem Involvement of mu-opiate receptors in ethanol-induced accumbal dopamine response(2003-08) Tang, Man Amanda, 1972-; Gonzales, Rueben AnthonyThe goal of this dissertation was to investigate the role of µ-opiate receptors in the regulation of ethanol-induced accumbal dopamine release using µ-opiate receptor knockout mice. Accumbal dopamine response to ethanol (2 g/kg, intraperitoneal injection, i.p.) was characterized in one of the parental strains that the knockout mice were developed on, C57BL/6; two strains of µ-receptor knockout mice (C57BL/6 x 129SvEv, C57BL/6 background); and the mixed genetic background mice pretreated with µ1-receptor antagonist, naloxonazine. Ethanol increases accumbal dopamine release in both male and female C57BL/6 mice. Thus, the C57BL/6 strain is a justifiable model system for studying the mechanisms involved in ethanol regulation of mesolimbic dopamine activity. Habituation to the i.p. procedure is required to detect a significant increase in accumbal dopamine response compared with saline controls in males. Therefore, it was routinely used for the remaining experiments. Accumbal dopamine response to ethanol was abolished in female, not in male knockout mice (C57BL/6 x 129SvEv). Similar results were obtained in the mixed genetic background mice that were pretreated with naloxonazine. The similarity of the results from the naloxonazine study to that of the knockout model suggests the absence of neurochemical compensations due to gene deletion. Finally, a decrease in accumbal dopamine release induced by ethanol was observed in both male and female knockout mice (C57BL/6). The gender difference seen in the mixed genetic background knockout mice may be due to the influence of one of the parental strains, 129SvEv, on the hybrid strain of the knockout mice. The results with both gene deletion and pharmacological blockade of the µ- opiate receptor support the hypothesis that µ-opiate receptors are a critical component of the mechanism by which ethanol stimulates accumbal dopamine release.Item Prefrontal cortex D1 receptor regulation of mesolimbic dopamine and cocaine self-administration(2004) Olsen, Christopher Mark; Duvauchelle, Christine L.