TY - JOUR
T1 - Nature of seasonal variation in development of acute tolerance to morphine
AU - Shoham-Moshonov, Sandra R.
AU - Weinstock, Marta
PY - 1977/5/15
Y1 - 1977/5/15
N2 - Morphine inhibits contractions of coaxially stimulated guinea pig ileum. Acute tolerance to this effect occurs on continuous perfusion with morphine for 1.5 h. This is associated with an increase in the sensitivity of the tissue to acetylcholine. Acute tolerance does not always develop in spite of identical treatment, but shows a distinct seasonal incidence. It is significantly higher in the summer (May-Nov.) than winter (Dec.-April). This seasonal variation in development of tolerance does not appear to be related to changes in diet, environmental light or temperature, or to the sensitivity of the ileum to morphine. In the winter, the acetylcholine release from stimulated ilea is lower than in the summer. In addition to inhibiting acetylcholine release, morphine also has a non-specific blocking effect in the winter. This postjunctional effect could prevent the development of supersensitivity to acetylcholine during continuous morphine treatment so that acute tolerance cannot occur.
AB - Morphine inhibits contractions of coaxially stimulated guinea pig ileum. Acute tolerance to this effect occurs on continuous perfusion with morphine for 1.5 h. This is associated with an increase in the sensitivity of the tissue to acetylcholine. Acute tolerance does not always develop in spite of identical treatment, but shows a distinct seasonal incidence. It is significantly higher in the summer (May-Nov.) than winter (Dec.-April). This seasonal variation in development of tolerance does not appear to be related to changes in diet, environmental light or temperature, or to the sensitivity of the ileum to morphine. In the winter, the acetylcholine release from stimulated ilea is lower than in the summer. In addition to inhibiting acetylcholine release, morphine also has a non-specific blocking effect in the winter. This postjunctional effect could prevent the development of supersensitivity to acetylcholine during continuous morphine treatment so that acute tolerance cannot occur.
KW - Acetylcholine release
KW - Guinea pig ileum
KW - Morphine tolerance
KW - Seasonal variation
UR - http://www.scopus.com/inward/record.url?scp=0017702193&partnerID=8YFLogxK
U2 - 10.1016/0014-2999(77)90127-3
DO - 10.1016/0014-2999(77)90127-3
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C2 - 872871
AN - SCOPUS:0017702193
SN - 0014-2999
VL - 43
SP - 153
EP - 161
JO - European Journal of Pharmacology
JF - European Journal of Pharmacology
IS - 2
ER -