PAIN SENSITIVITY AND SACCHARIN INTAKE IN ALCOHOL-PREFERRING AND ALCOHOL-NONPREFERRING RAT STRAINS

The experiments were designed to study the association between consump tion of palatable 0.1% (w/v) saccharin solution, voluntary drinking of 10% (v/v) ethanol solution, and pain sensitivity measured with the ho t plate test. Rat lines that were genetically selected for high alcoho l consumption (P and AA rats), alcohol-preferring Fawn Hooded (FH) rat s and their F2[FH x FRL] hybrids, and the Maudsley Nonreactive strain (MNRA) had a high propensity to consume saccharin that resulted in a s ignificant (almost twofold; p < 0.05) increase in their daily fluid in take when saccharin was available. These strains also had lower pain t hresholds in the hot plate test than did their parallel strains [NP, A NA, Maudsley Reactive (MR)]. Most alcohol-nonpreferring strains [NP, A NA, and Flinders Resistant Line (FRL)] had preference ratios for sacch arin about as high as those of the alcohol-preferring rats but, unlike the high alcohol drinkers, they did not increase their total fluid in take when saccharin was available. The mean saccharin intakes of the l ines were strongly correlated with their alcohol drinking during the f irst 5 days, whereas their latencies on the hot plate were inversely r elated to their change in alcohol drinking with experience. The result s are consistent with an endogenous opioid mechanism being involved in alcohol drinking.