The mesolimbic dopamine system, including dopaminergic projections from the ventral tegmental area (VTA) to nucleus accumbens (NAc), is critically involved in the development of addiction to many drugs of abuse, including cocaine (CA). Although there is an attractive hypothesis that the modifications of mesolimbic reward circuit following repeated drug exposure are responsible for cocaine-addicted causes behaviors change, however, our understanding in the underlying molecular mechanisms at the neural circuit level is still in its infancy. It has been suggested PKMzeta, a constitutively active atypical isoform of PKC, plays a critical role in spatial memory formation and long-term synaptic potentiation in hippocampus. To define the relationship among PKMzeta, CA-induced synaptic long-term potentiation and CA addiction, we examined the regulation of PKMzeta after CA administration in Sprague-Dawley rat. We found single CA injection elicits an increase in PKMzeta protein expression in the VTA region. The increase was first observed 10 min after CA administration and lasted for 7 days, the longest sampling time point of our experimental design. The PKMzeta protein expression can also be induced in 10 minutes while incubating the acute isolated brain slice with CA, the expression within 1 hr can be eliminated at the present of Chelerythrine (PKC inhibitor) and ZIP (PKMzeta inhibitor) suggests a positive feedback loop. The PKMzeta mRNA expression can be induced within 1 hr, and Actinomycin d (transcription inhibitor) had no effect on the PKMzeta protein expression indicating CA increases PKM£a translation from preexisting PKM£a mRNA. Furthermore,real time PCR-based analysis showed resembling increase profile ofPKM£a mRNA after single CA injection, suggesting a co-upregulation of transcription and translation of PKM£a after CA administration in VTA.
Eticlopride (dopamine receptor D2-subtype antagonist) ¡BSCH-23390(dopamine receptor D1-subtype antagonist)¡BH-89 (PKA inhibitor)¡B
Wortmannin (PI3K inhibitor)¡BPD98059 (MEK1 inhibitor) decreasedcocaine-induced PKM£a expression within 1 hr in VTA. On the contrary,
KN-62 (CaMK II inhibitor) has no obvious effect on PKM£a expression.
CA challenge not only induces the PKM£a expression in the VTA region but also in the NAc and hippocampus region. The CA-induced PKM£a
expression is more obvious in elder group (>45 days in age) than younger group (18~30 days in age), similar results also showed in the locomotor
activity assay. Prenatal CA exposure decreased the postnatal CA-induced PKM£a expression and the locomotor sensitivity in younger group.
Overall, results from our current experiments have raised the possibility of PKM£a involvement in CA addiction. How CA regulates PKM£a
expression and the context dependence between PKM£a and CA-induced behavior change and synaptic long-term potentiation remains further elucidation.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0801110-184540 |
| Date | 01 August 2010 |
| Creators | Chang, Yu-Hua |
| Contributors | Jau-Cheng Liou, Ing-Jun Chen, Ming-Hung Tai, Ching-Mei Hsu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0801110-184540 |
| Rights | not_available, Copyright information available at source archive |
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