CYP2D6 metabolizes codeine to morphine, the active analgesic metabolite. Variation in brain CYP2D6 activity may affect brain morphine levels after codeine administration and thereby influence analgesia. We investigate the effect of inhibiting brain CYP2D on codeine-induced analgesia. METHODS: Rats received intracerebroventricular (i.c.v.) injections of CYP2D inhibitors or vehicle controls. Rats were then given subcutaneous codeine injections and analgesia was measured with the tail-flick test. Morphine and codeine concentrations in brain and plasma were measured. CYP2D activity in brain and liver were assessed in vitro. RESULTS: Compared to vehicle treatment, i.c.v. inhibitor treatments resulted in lower codeine-induced analgesia, lower morphine levels in brain but not in plasma after codeine injections, and lower CYP2D activity in brain membranes but not in liver microsomes. CONCLUSIONS: Inhibiting brain CYP2D reduces codeine’s metabolism to morphine, resulting in less analgesia. Variation in brain CYP2D6 activity may influence response to codeine and other CYP2D6 substrates.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/33628 |
| Date | 27 November 2012 |
| Creators | Zhou, Kaidi |
| Contributors | Tyndale, Rachel |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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