Inescapable shock-induced potentiation of morphine analgesia in rats: Sites of action

    Authors

    S. E. Hammack; C. E. Hartley; S. E. Lea; S. F. Maier; L. R. Watkins;L. C. Sutton

    Comments

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    Abbreviated Journal Title

    Behav. Neurosci.

    Keywords

    NUCLEUS RAPHE MAGNUS; FREELY MOVING CATS; SEROTONIN-CONTAINING NEURONS; DORSAL RAPHE; PERIAQUEDUCTAL GRAY; BRAIN-STEM; INDUCED ANTINOCICEPTION; PAIN MODULATION; 5-HT METABOLISM; INTERFERENCE; Behavioral Sciences; Neurosciences

    Abstract

    Inescapable shock (IS) enhances analgesia to systemic morphine (MOR) 24 hr later. IS activates serotonin neurons in the dorsal raphe nucleus (DRN), rendering them hyperexcitable. These studies tested whether IS potentiates the analgesic effect of MOR microinjected in the DRN, as predicted by this hypothesis. To test site specificity, the effect of previous IS was examined on MOR microinjected lateral to the DRN and into 2 other sites that support MOR analgesia, the nucleus raphe magnus (NRM) and spinal cord. Twenty-four hours after IS, potentiated analgesia was observed after 0.5 mu g MOR microinjected into, but not lateral to, the DRN. Potentiated analgesia was also observed after NRM (1.0 mu g) and spinal cord (3.0 mu g) MOR microinjections. These data suggest that IS-induced excitability changes within the DRN synergize with opiates microinjected in other analgesia areas and that this potentiates the responses to opiates 24 hr after IS.

    Journal Title

    Behavioral Neuroscience

    Volume

    113

    Issue/Number

    4

    Publication Date

    1-1-1999

    Document Type

    Article

    Language

    English

    First Page

    795

    Last Page

    803

    WOS Identifier

    WOS:000082538700014

    ISSN

    0735-7044

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