The differential effects of lithium chloride and morphine on schedule-induced polydipsia: Implications for its use as an animal model of drug abuse

It has been suggested that the reinforcing properties of recreational compounds become salient under schedules of spaced feeding. If so, it might be expected that such compounds would be relatively ineffective in producing aversions under these conditions. This was tested in Experiment 1 in which schedule-induced saccharin consumption was followed by either vehicle, 10 mg/kg morphine or 0.6 mEq LiCl. Although both morphine and LiCl suppressed SIP, morphine produced a significantly weaker suppression than LiCl. Using a massed feeding design in which animals received all pellets in a single meal, Experiment 2 determined that morphine and LiCl were equally effective in inducing aversions, suggesting that the two compounds have comparable aversive effects under food deprivation. Together these data are consistent with the position that the reinforcing effects of recreational drugs become salient under SIP and affect their ability to condition aversions. This procedure may compounds.