Discriminative stimulus properties of ICSS in rats: Effects of ethanol and RO 15‐4513

AbstractRats were implanted with stimulating electrodes aimed at the medial forebrain bundle–lateral hypothalamus and trained in a discrete trial procedure to make a differential response (right or left lever press) in the presence or absence of brain stimulation. When animals reached 95% accuracy in this discrimination, testing with vehicle, ethanol (0.1, 0.3, 0.56, 1.0, g/kg), and ethanol plus RO 15‐4513 (1.0 mg/kg) began. During test sessions intermediate stimulus currents were programmed and the data comprised the number of trials completed on the stimulation‐appropriate lever as a function of intermediate currents. The stimulus current at which 50% of the trials were completed was defined as the detection threshold. Ethanol, at 1.0 g/kg, increased the detection threshold but also increased the time to complete the session and decreased the total number of lever presses. RO 15‐4513 reversed the increase in the detection threshold and reduced the increase in time to complete the session and reduced the decreases in lever presses. However, RO 15‐4513 alone, like ethanol, increased the time to complete the session and decreased the total number of lever presses. Thus, while RO 15‐4513 reverses some of the behavioral effects of ethanol, it also has its own behavioral effects, even at low doses.