Analgesia produced by microinjection of baclofen and morphine at brain stem sites

https://doi.org/10.1016/0014-2999(79)90102-XGet rights and content

Abstract

Microinjection of either baclofen (1.5 μg) or morphine (2.5 μg), in equimolar doses (14 mM), at sites located in the caudal periaqueductal gray (PAG) resulted in a delay in tail flick latency (analgesia). The relative analgesic potency of baclofen among caudal PAG sites, however, did not correlate with that of morphine. Application of either drug into the caudal aspect of the cerebral aqueduct also produced analgesia, but neither agent caused analgesia when applied at PAG sites rostral to the interaural line. Baclofen alos produced analgesia when microinjected in the lower brain stem at sites lateral to the midline in or near the nucleus gigantocellularis, but did not produce analgesia when applied on the midline at sites located within or near the raphe magnus. Conversely, morphine produced analgesia when applied locally at midline sites but not at sites located lateral to the midline. These data suggest that the analgesia produced by systemic administration of baclofen and morphine involves activation of different neuronal substrates.

References (29)

  • A. Herz et al.

    Activities and sites of antinociceptive action of morphine0like analgesics and kinetics of distribution following intravenous, intracerebral and intraventricular application

    Advan. Drug Res.

    (1971)
  • Y.F. Jacquet et al.

    Morphine action at central nervous system sites in rat: analgesia or hyperalgesia depending on site and dose

    Science

    (1973)
  • Y.F. Jacquet et al.

    Paradoxical effects after microinjection of morphine in the periqueductal gray matter in the rat

    Science

    (1974)
  • Y.F. Jacquet et al.

    The C-fragment of β-lipotropin: an endogenous neuroleptic or antipsychotogen?

    Science

    (1976)
  • Cited by (0)

    View full text