Effects of morphine and naloxone on Renshaw cells and spinal interneurones in morphine dependent and non-dependent rats.
The effects of microelectrophoretically administered morphine, naloxone, levorphanol and dextrorphan have been investigated on Renshaw cells and interneurones in the spinal cord of morphine-dependent and non-dependent anaesthetized rats. Morphine excited cholinoceptive neurones and enhanced the excitatory actins of acetylcholine and L-glutamate. This action of morphine appeared to be stereospecific and was antagonized by naloxone. Naloxone also antagonized acetylcholine-induced excitation but not L-glutamate-induced excitation. In dependent rats morphine was a more effective excitant of cholinoceptive neurones and naloxone was more effective as an antagonist of acetylcholine-induced excitations. These observations were interpreted as indicating that cholinergic mechanisms may be involved in morphine dependence and  naloxone-precipitated abstinence.
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D003917:Dextrorphan / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D005971:Glutamates / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D006801:Humans; D007395:Interneurons / Q000187:drug effects; D007981:Levorphanol / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009021:Morphine Dependence / Q000503:physiopathology*; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011930:Reaction Time / Q000187:drug effects; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D005971:Glutamates; D003917:Dextrorphan; D007981:Levorphanol; D009270:Naloxone; D005680:gamma-Aminobutyric Acid; D009020:Morphine; D000109:Acetylcholine; D005998:Glycine