Oral etonitazene and cocaine consumption by AA, ANA and Wistar rats

It has been previously suggested that drug-seeking behavior maintained by alcohol, opioids, and cocaine may have some common genetic determinants. Therefore, the present study examined the intake of etonitazene, a potent opioid agonist, and cocaine by alcohol-preferring AA (Alko, Alcohol), alcohol-avoiding ANA (Alko, Non-alcohol), and Wistar rats in a two-bottle choice test. The animals, housed in single cages, were given a choice between tap water and ascending concentrations of etonitazene (0.5, 1.0, 2.0, and 4.0 micrograms/ml) or cocaine (0.2, 0.4, 0.8, and 1.6 mg/ml) solutions prepared in water. Finally, to assess the sensitivity to bitter taste by these strains, a quinine preference test with ascending quinine concentrations was conducted. The clearest line differences were found with etonitazene: at all concentrations, the AAs consumed significantly more etonitazene than the ANAs and Wistars that showed no differences. The highest etonitazene intake by the AAs, 181 micrograms/kg/day at the concentration of 4.0 micrograms/kg, produced apparent signs of opioid intoxication and withdrawal. The AAs also drank more cocaine solution than the other lines. Since, however, the pattern of cocaine intake as a function of concentration resembled that with quinine, the line differences in cocaine consumption may partly be accounted for by the differential sensitivity to bitter taste by the lines. In contrast, the marked line differences in the intake of the etonitazene solutions, which had only a slightly bitter taste, seem more likely to have been produced by the post-ingestional effects of the opioid.