A demonstration of naloxone-precipitated opiate withdrawal on single neurones in the morphine-tolerant/dependent rat brain.
1 A comparison has been made between the effects of microelectrophoretically applied naloxone on single neurones in the frontal cerebral cortex and the striatum of naive and of morphine-tolerant/dependent rats, anaesthetized with a mixture of alpha-chloralose and urethane. 2 Specificity of the results obtained was evaluated by contrasting the effects of alternate applications of the (+)- and (-)-isomers of naloxone to the same neurones. 3 In naive rats naloxone had predominantly no effect, only a few cells revealing non-specific depressant responses to the drug. 4 In morphine-tolerant/dependent rats a higher proportion of neurones responded to naloxone; either with stereospecific excitatory responses, in which the activity evoked by L-glutamate or acetylcholine was increased, or with a non-specific inhibition, similar to that observed in naive animals. 5 It is suggested that these excitatory responses to microelectrophoretically applied (-)-naloxone represent opiate withdrawal responses at the single neurone level and that they reflect a latent hyperexcitability of the postsynaptic membrane in the morphine-tolerant/dependent state.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006801:Humans; D008297:Male; D009021:Morphine Dependence / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*
D005971:Glutamates; D009270:Naloxone; D018698:Glutamic Acid; D000109:Acetylcholine