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THE EFFECTS OF MICROIONTOPHORETICALLY APPLIED MORPHINE AND TRANSMITTER SUBSTANCES IN RATS DURING CHRONIC TREATMENT AND AFTER WITHDRAWAL FROM MORPHINE
Author(s) -
BRADLEY P.B.,
DRAY A.
Publication year - 1974
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1974.tb09638.x
Subject(s) - morphine , tachyphylaxis , acetylcholine , chemistry , pharmacology , anesthesia , medicine
The effects of microiontophoretically applied acetylcholine, noradrenaline, 5‐hydroxytryptamine and morphine were studied on single brain stem neurones of rats during chronic morphine pretreatment and 24 h after its withdrawal. No significant changes were observed in the initial spontaneous neuronal firing rate or in the qualitative or quantitative effects of acetylcholine, noradrenaline or 5‐hydroxytryptamine. However, in chronically treated animals there was a significant decrease in the number of neurones excited by morphine or showing tachyphylaxis to morphine on repeated microiontophoretic applications. We suggest that some of the cellular central nervous system changes which occur during chronic morphine treatment are reflected by the decrease in sensitivity of neurones to morphine excitation.