Intermittent and chronic morphine treatment induces long-lasting changes in δ-opioid receptor-regulated acetylcholine release in rat striatum and nucleus accumbens

Intermittent treatment of rats with morphine (10 mg/kg s.c., once daily) caused an increase (of about 30%) of the electrically evoked release of [ 14C]acetylcholine from cholinergic interneurons of superfused striatal slices 1–21 days after morphine withdrawal. Similarly, chronic treatment with esca...

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Bibliographic Details
Published in:European journal of pharmacology 1995-09, Vol.283 (1), p.169-176
Main Authors: Tjon, Guno H.K., De Vries, Taco J., Nestby, Patrizia, Wardeh, George, Mulder, Arie H., Schoffelmeer, Anton N.M.
Format: Article
Language:English
Subjects:
Acetylcholine - metabolism
Acetylcholine release
Animals
Biological and medical sciences
Cholinergic Fibers - drug effects
Corpus Striatum - drug effects
Drug addictions
Male
Medical sciences
Morphine
Morphine - pharmacology
Nucleus accumbens
Nucleus Accumbens - drug effects
Opioid receptor
Rats
Rats, Wistar
Sensitization
Sodium Chloride - pharmacology
Striatum
Time Factors
Toxicology
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Summary:Intermittent treatment of rats with morphine (10 mg/kg s.c., once daily) caused an increase (of about 30%) of the electrically evoked release of [ 14C]acetylcholine from cholinergic interneurons of superfused striatal slices 1–21 days after morphine withdrawal. Similarly, chronic treatment with escalating doses of morphine (5–50 mg/kg s.c., 3 times daily), causing physical dependence (unlike intermittent treatment), resulted in an enduring enhanced response of these neurons towards depolarization. Following chronic morphine treatment this adaptive increase of acetylcholine release was associated with a slight but long-lasting decrease of the (δ-opioid receptor-mediated) maximal inhibitory effect of [Met 5]enkephalin, whereas upon intermittent drug treatment δ-opioid receptor desensitization was observed 1 day after opiate withdrawal only. Also in slices of the nucleus accumbens both intermittent as well as chronic morphine administration caused a long-lasting increase of the electrically evoked [ 14C]acetylcholine release. Therefore, we hypothesize that an enhanced (re)activity of striatal and accumbal cholinergic neurons, which are regulated by dopaminergic neurons of the ventral mesencephalon, may represent a long-lasting neuroadaptive effect of morphine (and possibly other drugs of abuse) playing a crucial role in behavioral sensitization associated with enhanced vulnerability to drugs of abuse.
ISSN:0014-2999
1879-0712
DOI:10.1016/0014-2999(95)00319-G