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THE EFFECTS OF ACUTELY ADMINISTERED ANALGESICS ON THE TURNOVER OF NORADRENALINE AND DOPAMINE IN VARIOUS REGIONS OF THE RAT BRAIN
Author(s) -
SUGRUE M.F.
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.tb09696.x
Subject(s) - pentazocine , dopamine , morphine , (+) naloxone , endocrinology , medicine , chemistry , dextrorphan , pharmacology , opioid , receptor
1 Noradrenaline and dopamine turnover rates were determined following blockade of synthesis by α‐methyl‐ p ‐tyrosine. Morphine, pentazocine and methadone had no effect on steady state levels or on turnover of noradrenaline in whole brain and in the hypothalamus. Although morphine was without action on medulla‐pons noradrenaline steady state levels, a drug‐induced increase in turnover rate was observed which was antagonized by pretreatment with naloxone (5 mg/kg). Pentazocine and methadone failed to alter either the steady state level of noradrenaline in the medulla‐pons or its turnover rate. 2 Morphine accelerated the decline in striatal α‐methyl‐ m ‐tyramine levels following subcutaneous injection of α‐methyl‐ m ‐tyrosine 18 h previously. 3 All three drugs increased the turnover of dopamine in whole brain and corpus striatum although the striatal effect was prevented by naloxone pretreatment. The minimum doses of morphine, pentazocine and methadone required to elicit a significant effect on striatal dopamine turnover were 10 mg/kg, 30 mg/kg and 10 mg/kg respectively. 4 The possibility of a dopaminergic involvement in the antinociceptive effect of analgesics is discussed.