On the involvement of GABA in the analgesia produced by baclofen, muscimol and morphine

Neuropharmacology. 1982 May;21(5):397-403. doi: 10.1016/0028-3908(82)90022-3.


In the mouse hot-plate test (50 degrees C), muscimol produced analgesia which was blocked by bicuculline but not by picrotoxin. Analgesia produced by baclofen was dose-dependent and stereoselective, but was not blocked by bicuculline, picrotoxin or naloxone. Morphine-induced analgesia was not altered by bicuculline. The inhibitors of GABA-transaminase, amino-oxyacetic acid, gamma-acetylenic GABA and gamma-vinyl GABA, produced analgesia which was much more prolonged than that observed with muscimol, baclofen or morphine. The analgesic action of these agents was not significantly altered by bicuculline. At a higher plate temperature (55 degrees C), GABA-transaminase inhibitors produced minimal analgesia but significantly enhanced the analgesic action of baclofen. gamma-Vinyl GABA markedly increased both the peak effect and the duration of analgesia but gamma-acetylenic GABA and amino-oxyacetic acid caused smaller increases. In the mouse hot-plate test, bicuculline-sensitive GABA receptors appear to mediate the analgesic action fo muscimol. Analgesia produced by baclofen, morphine and inhibitors of GABA-transaminase may involve another class of GABA receptors which are insensitive to bicuculline.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Aminobutyrate Transaminase / metabolism*
  • Analgesia*
  • Analgesics
  • Animals
  • Baclofen / pharmacology
  • Bicuculline / pharmacology
  • Male
  • Mice
  • Muscimol / pharmacology
  • Naloxone / pharmacology
  • Picrotoxin / pharmacology
  • Transaminases / metabolism*
  • gamma-Aminobutyric Acid / physiology*


  • Analgesics
  • Picrotoxin
  • Muscimol
  • Naloxone
  • gamma-Aminobutyric Acid
  • Transaminases
  • 4-Aminobutyrate Transaminase
  • Baclofen
  • Bicuculline