(a)
(b)
Figure 2: (a) Experimental timeline for naltrexone antagonism of U50,488-induced reinstatement. Rats () were trained to self-administer ethanol, and then lever pressing was extinguished. Following extinction, rats were pretreated with naltrexone (3.0 mg/kg, s.c.) or saline 30 min prior to testing. Rats were then injected with U50,488 (0.1–1.0 mg/kg, i.p.) or saline 10 min prior to testing. Test sessions were conducted every 3-4 days, with rats experiencing extinction sessions daily between test days. (b) Experimental timeline for nor-BNI antagonism of U50,488-induced reinstatement. Stable self-administration levels were reestablished following the experiment described in (a) and then extinguished. Following extinction, rats were pretreated with a single saline injection. 24 h later rats were injected with a U50,488 (0.1–1.0 mg/kg, i.p.) or saline 10 minutes prior to testing. Test sessions were repeated every 3-4 days with rats experiencing extinction sessions daily between test days. After all doses of U50,488 were tested, rats were given a single injection of nor-BNI (20 mg/kg, i.p.). 24 h later, rats were injected with U50,488 (0.1–1.0 mg/kg, i.p.) or saline 10 minutes prior to testing. Test sessions were repeated every 3-4 days with rats experiencing extinction sessions daily between test days.