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BLOCKADE OF STRIATAL NEURONE RESPONSES TO MORPHINE BY AMINOPHYLLINE: EVIDENCE FOR ADENOSINE MEDIATION OF OPIATE ACTION
Author(s) -
PERKINS MARTIN N.,
STONE TREVOR W.
Publication year - 1980
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.1476-5381.1980.tb10892.x
Subject(s) - aminophylline , morphine , adenosine , excitatory postsynaptic potential , inhibitory postsynaptic potential , (+) naloxone , chemistry , opiate , pharmacology , adenosine receptor , medicine , endocrinology , neuroscience , receptor , opioid , biology , agonist , biochemistry
1 The responses of cortical and striatal neurones to morphine and adenosine applied iontophbretically have been studied in the male rat. 2 The majority of cells (57%) within the corpus striatum were profoundly inhibited, and a smaller proportion (18%) excited by morphine. Adenosine depressed the firing rate of 30/44 cells in the striatum, excitation never being observed. In contrast, the responses of cortical cells to morphine were typically weak and required longer ejection pulses to effect comparable changes in firing rate. 3 Aminophylline applied iontophoretically, as an anion, proved able to antagonize reversibly both morphine and adenosine in parallel. 4 On a number of cells, γ‐aminobutyric acid (GABA) was used as a control depressant but aminophylline did not appear to reduce these responses. 5 The responses to morphine (both inhibitory and excitatory) were not easily antagonized by naloxone. Typically, excitatory responses were easier to antagonize than the inhibitory ones. 6 It is concluded that a consequence of the interaction of morphine with its receptors may be the release of adenosine which subsequently produces the inhibition observed with morphine.