Does morphine enhance the release of 5-hydroxytryptamine in the rat spinal cord? An in vivo differential pulse voltammetry study.
Differential pulse voltammetry used in combination with an electrochemically treated carbon fiber electrode allowed the detection of 5-hydroxyindoles (5-HI) in the dorsal horn of the urethane-anesthetized rat. Voltammograms were recorded every 3 min for up to 4 h. One component of the signal, peak 3, corresponding to 5-HI and uric acid was first identified separately in vitro as well as in vivo, and then further examined by means of systemic L- and D-trytophan administration and by local application of uricase, respectively. It was found that the height of peak 3 was unaffected by systemic morphine. Even following pretreatment with probenecid, the height of peak 3 was increased only 8.6-13.7% over that with saline, by morphine given either intraperitoneally or intracerebrally into the nucleus raphe magnus. However, these increments of peak 3 were not statistically significant. These findings suggest that the serotonin descending system is unlikely to play an important role in morphine analgesia.
D000818:Animals; D004563:Electrochemistry; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D011339:Probenecid / Q000494:pharmacology; D011903:Raphe Nuclei / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects* / Q000378:metabolism; D013237:Stereoisomerism; D014364:Tryptophan / Q000494:pharmacology; D014503:Urate Oxidase / Q000494:pharmacology
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D009020:Morphine; D014364:Tryptophan; D014503:Urate Oxidase; D011339:Probenecid