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Effects of Ethanol and Ethanol Withdrawal on Nociception in Rats
Author(s) -
Gatch Michael B.,
Lal Harbans
Publication year - 1999
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1111/j.1530-0277.1999.tb04118.x
Subject(s) - ethanol , nociception , hyperalgesia , liquid diet , tail flick test , anesthesia , chemistry , radiant heat , drug tolerance , self administration , pharmacology , medicine , biochemistry , receptor , materials science , composite material
The effect of acute and chronic administration of ethanol and ethanol withdrawal on a radiant heat tail‐flick assay of nociception was examined in rats. Acute administration of ethanol (2.0 g/kg, ip) produced peak antinociception (68% of maximum) by 30 min, and effects were gone by 120 min. Cumulative doses of ethanol (0.5–2.0 g/kg, ip) produced dose‐dependent increases in latencies to 49% of maximum. During chronic administration, a liquid diet containing ethanol (6.5%) was given for 10 days. Tail‐flick latencies were measured on day 0 (baseline), day 2, 4, 6, 8, and 10 of chronic ethanol and at 3, 6, 12, and 36 hr after removal of ethanol. To test for behavioral tolerance, both between‐ and within‐group designs were used. In both between‐ and within‐group experiments, the antinociceptive effects of chronic ethanol peaked by day 4 of exposure to the liquid diet, and tolerance developed by day 10. When the liquid diet was removed, hyperalgesia was detected at 6 and 12 hr after withdrawal, and was gone by 36 hr after withdrawal. When cumulative doses of ethanol (0.5–2.0 g/kg) were administered starting 12 hr after withdrawal, ethanol (0.5 g/kg) fully reversed the hyperalgesia induced by ethanol withdrawal, even though this dose was without antinociceptive effect in the absence of withdrawal. Higher doses of ethanol during ethanol withdrawal did not increase tail‐flick latencies over baseline. In summary: (1) ethanol produces antinociception when administered acutely or chronically; (2) tolerance to the antinociceptive effects develops during chronic administration; (3) ethanol withdrawal induced hyperalgesia, which was reversed by ethanol; and (4) repeated testing did not produce behavioral tolerance.