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. 1978 Mar 1;56(2):133-7.
doi: 10.1007/BF00431838.

Effects of medial raphe and raphe magnus lesions on the analgesic activity of morphine and methadone

W T Chance, G M Krynock, J A Rosecrans

Effects of medial raphe and raphe magnus lesions on the analgesic activity of morphine and methadone

W T Chance et al. Psychopharmacology (Berl). .

Abstract

The effects of lesions of the raphe nuclei on opiate-induced antinociception and brain serotonin (5-HT) levels were investigated. Lesions of the medial raphe nucleus effectively antagonized the analgesic effects of morphine, but not methadone, and lowered brain 5-HT. The decrement in analgesic activity of morphine was reversed by pretreatment with 5-hydroxytryptophan. Lesions of the raphe magnus, a descending 5-HT system, antagonized the analgesic potency of both morphine and methadone. These experiments indicate a differential effect of 5-HT manipulation on opiate-induced analgesia, suggesting a different mechanism of analgesic action for morphine and methadone.

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