Contrasting effects of acute vs. chronic tricyclic antidepressant treatment on central morphine analgesia

Document Type

Article

Publication Date

1984

Abstract

Antinociception following central opioid microinjection in rats was assessed weekly via a tail-flick procedure during chronic tricyclic antidepressant (TCA) treatment. (1) Daily TCA: Subcutaneous injections of desipramine (DMI), 30 mg/kg, chlorimipramine (CMI), 10 mg/kg, or saline, 1 ml/kg, were given daily for 22 days. Morphine sulfate (M), 5 μg, was microinjected into the ventrolateral periaqueductal gray (VLPAG) at 7 day intervals. On day 1, DMI or CMI enhanced M analgesia whereas saline did not. Augmentation of M disappeared by days 8 and 15 for CMI and DMI, respectively and was replaced by attenuation which was still observed on day 22 for both TCAs. l-Tryptophan (LT), 100 mg/kg i.p., on days 15 and 22 temporarily restored TCA enhancement of M. Fourteen days after cessation of all daily TCA treatments, enhancement of M by CMI was similar to that observed on day 1, whereas recovery of DMI-induced facilitation was incomplete. (2) Weekly TCA: Weekly treatment with DMI, CMI, or saline in the same doses as above had similar effects. M analgesia was enhanced by the TCAs but not saline on day 1 ; this facilitation was absent by day 15. Attenuation of M by DMI or CMI was evident on day 22; 2 weeks after cessation of all weekly TCA treatments, complete recovery of TCA-induced augmentation was observed. Loss of M facilitation during chronic daily or weekly TCA administration may be related to reduction of central opioid and/or 5-HT2 receptors. © 1984.

Publication Title

Pain

Volume

20

Issue

4

First Page

323

Last Page

334

Comments

This article was published in Pain, Volume 34, Issue 1, Pages 85-92.

The published version is available at http://dx.doi.org/10.1016/0304-3959(88)90185-6.

Copyright © 1988.

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