Behavior and drug measurements in Long-Evans and Sprague-Dawley rats afterethanol-cocaine exposure

Long-Evans and Sprague-Dawley rats show differential behavioral responses t o cocaethylene, a metabolite derived from the simultaneous ingestion of eth anol and cocaine. Such differences may also be manifested when these outbre d strains are exposed to ethanol and cocaine. To test this hypothesis, both strains were fed an ethanol-diet (8.7% v/v) in conjunction with cocaine (1 5 mg/kg) injections for 15 days. The following parameters were evaluated: ( a) ethanol consumption, (b) cocaine-induced behavioral activity, (c) blood ethanol levels, (d) blood, liver, or brain cocaine and cocaethylene levels, and (e) liver catalase and esterase activity. We found that Long-Evans rat s drank significantly more of the ethanol diet relative to the Sprague-Dawl ey line during the first few days of the test session. This rat phenotype a lso differed significantly from the Sprague-Dawley line in terms of behavio ral activity after cocaine administration. Blood ethanol levels did not dif fer between strains. Similarly, we failed to detect strain-dependent differ ences in blood, liver, or brain cocaine levels as measured by gas chromatog raphy/mass spectrometry. Cocaethylene levels, however, were higher in blood and brain of Long-Evans relative to Sprague-Dawley cohorts. Although the e thanol-cocaine regimen produced a marked suppression of catalase and estera se activity compared with control-fed rats, this suppression was roughly eq uivalent in both rat phenotypes. These data are discussed in the context of genotypic background and vulnerability to polysubstance abuse. (C) 1999 El sevier Science Inc.