The Regulation Of AMPARs Trafficking And Degration In Striatum Controls Animal Behavioral Adaptations To Cocaine

Part I The Role of AMPA Receptor Trafficking in the Nucleus Accumbens in the Expression of Locomotor Sensitization to CocaineAim:Strong evidence has accumulated to support a requirement for glutamate transmission in the development of behavioral sensitization. An increasing amount of literature indicates that repeated contingent or non-contingent exposure to cocaine followed by an abstinence period increases synaptic AMPAR levels in the NAc. However, subsequent studies indicate that the nature of increased synaptic AMPARs in behavioral sensitization is more complex than it seems. NSF-GluA2interactions are shown to be important to maintain AMPA-mediated transmission at the synapses. However, until now, there are few reports about the role of NSF-GluA2interactions in locomotor sensitization.Methods:Locomotor activity was recorded in locomotion cages by using AniLab Software. We used western blot analysis and BS3cross-linking to detect surface expression of GluA2. We used immunostaining to detect the proportion of GluA2colocalized with NSF. We used coimmunoprecipitation to detect NSF-GluR2interactions.Results:We first established a rat model of behavioral sensitization by repeated cocaine injection. Then, we used immunostaining experiments and found an increase in the proportion of GluA2colocalized with NSF in NAc neurons of sensitized rats compared with control rats. Moreover, our coimmunoprecipitation results revealed that NSF-GluA2interactions were significantly higher in cocaine-exposed rats than in saline-exposed ones (sal:100.00±16.82; coc:155.38±19.74; n=4per group, p< 0.05vs saline), providing further evidence for an increase in the NSF-GluA2binding in NAc neurons after withdrawal from cocaine. We used the specific NSF-GluA2interaction blocking peptide (pep-R845A conjugated to TAT) to determine the role of the increased binding of NSF to GluA2in cocaine sensitization. It was found that TAT-pep-R845A significantly increased the response to cocaine (aCSF+coc:23526.25±2002.80; TAT-pep+coc:22567.27±1900.80; TAT-pep-R845A+coc:30283.93±1987.42; n=6-12rats; p<0.01vs the other experimental groups). The level of surface GluA2was decreased after bath incubation of NAc slices from cocaine-exposed rats with TAT-pep-R845A (TAT-pep:100.00±6.04; TAT-pep-R845A:54.80±6.80; n=5rats; p<0.05vs control peptide) and intracranial injections of this peptide into the NAc produced the same effect (TAT-pep:100.00±9.40; TAT-pep-R845A:68.75±12.10; n=5rats for each group; p<0.05vs control peptide) as that seen when peptides were bath-applied to slices.Conclusion:The present study indicated that after withdrawal from noncontingent cocaine injections increased NSF-GluA2interactions in the NAc. Disrupted accumbal NSF-GluA2interactions enhanced the responses of rat to cocaine by inhibiting the surface expression of GluA2-containing AMPARs. These results supported our hypothesis that withdrawal-induced upregulation of NSF-GluA2interactions would be a compensatory mechanism to counteract cocaine psychomotor sensitization. Part II Degradation of AMPARs in dorsal stria tum controls cocaine intakeAim:The dorsal striatum is a key brain region regulating the development of compulsive cocaine use. In many common experimental situations, the the final common pathway for drug seeking involves glutamate inputs terminating on MSN in the NAc. However, motor circuitry involving the dorsal striatum becomes more important as drug use becomes habitual. Here we identify a role for AMPARs in regulating compulsive-like cocaine intake.Methods:We used cocaine self-administration to detect cocaine intake by using AniLab Software. We used Real-time PCR to detect mRNA levels of AMPARs. We used immunoblotting to detect protein levels of AMPARs, NMDARs and so on. We used intracerebral injection procedures to inject virus and drugs. We used immunostaining to detect LC3.Results:Chronic, long-term use of cocaine can result in addiction, which is characterized by a gradual loss of control over drug use. Here we reported that GluAl was downregulated in the dorsal striatum of rats with a history of prolonged access to cocaine (saline:100.00±5.69%; cocaine:60.00±2.07%; n=8rats; p<0.01vs saline). Overexpression of GluA1increased cocaine intake in rats (n=8-9rats for each group; p<0.05, p<0.01vs the same day in lenti-control rats). Self-administration of cocaine increased the level of LC3Ⅱ protein (saline:100.00±17.17%; cocaine limited:169.44±25.17%; cocaine prolonged:165.85±20.28%), and decreased the protein of p62(saline:100.00±5.35%; cocaine:35.23±3.30%; n=4-10rats for each group; p<0.05, p<0.01vs saline).