| Abstract No.: | C-B3030 |
| Country: | Canada |
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| Title: | COCAINE MODULATES THE IN VITRO EXPRESSION OF MOR AND NO PRODUCTION IN PC12 CELLS |
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| Authors/Affiliations: | 1 Warren Winick*; 1 Francesco Leri; 1 Bettina Kalisch;
1 University of Guelph, ON, Canada
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| Content: | Cocaine, a stimulant with many effects in the central nervous system, has been shown to alter the expression of μ opioid receptors (MORs) in humans and laboratory animals. Although the exact mechanism through which cocaine exerts its effect on MORs is not currently known, there is evidence suggesting that it may involve nitric oxide (NO)-depended intracellular signaling. To test this hypothesis, we employed a PC12 cell model to study in vitro expression of MOR, its modulation by cocaine, and the role of NO. Using Western immunoblotting, we determined that treatment with 50 ng/mL nerve growth factor (NGF), which increases NO synthase (NOS) activity and NO production, increased MOR expression following 72 h of treatment. This effect was blocked by pre-treatment with the NOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME). We then treated PC12 cells with cocaine for 72 h or for 1 h three times a day for 72 h, and found that MOR expression was higher following 50 µM cocaine in the first condition and 10 µM cocaine in the second. To determine the effect of cocaine exposure on NO production, we used a DAF-2DA fluorescence assay following the 72 h of cocaine treatment or NGF and cocaine co-treatment. In both conditions, NO production was higher following 10 and 50 µM cocaine treatment, however no increase was observed following 1 µM of cocaine. Finally, we explored whether the effect of cocaine on MOR expression was modulated by NO by pre-treating PC12 cells with L-NAME before cocaine treatment for 72 h or for 1 h three times a day for 72 h. Using Western immunoblotting, we found that L-NAME prevented cocaine-induced increases in both treatment conditions. The results of these studies indicate that cocaine increases MOR expression through increases in NO production.
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