Figure 2.

Voluntary alcohol intake, instrumental conditioning, and alcohol-seeking characterization in rP, rNP, and rHAD1 rats (second cohort). Rats from the second cohort were divided into two subgroups: some were exposed to alcohol in a 2-bottle choice procedure (EtOH-experienced, on the left), whereas others were screened for anxiety-like profile and stayed in their home cage for the same period of time (EtOH-naive, on the right). (a) The 10% alcohol intake (g/kg) and (b) percentage of alcohol preference over the total fluid intake (%) were assessed every 24 h using the 2-bottle choice procedure for 18 continuous days in rP (n=20), rNP (n=10), and rHAD1 (n=18) EtOH-experienced rats. In the meantime, EtOH-naive rats (n=10 rP rats; n=10 rNP rats) were assessed for anxiety-like behavior on the EPM. The % of time spent in the open arms (% time OA/(OA+CA), mean±SEM) and % of open arm entries (% entries OA/(OA+CA), mean±SEM) are shown in (c) and (d), respectively. All the animals (EtOH-experienced and EtOH-naive) were then instrumentally trained to seek 15% EtOH. Lever presses (mean±SEM) under FI15 (white bars) and under second-order schedule of reinforcement (diagonal bars) are shown in (e) and (f) in EtOH-experienced and EtOH-naive rats, respectively. Alcohol intake (g/kg) during the 20 min drinking period earned by responding during the FI15 schedule (white bars) and the second-order schedule of reinforcement (diagonal bars) are shown in (g) and (h) in EtOH-experienced and EtOH-naive rats, respectively. EtOH-naive rP rats were no different to EtOH-experienced rats in their acquisition of alcohol seeking (schedule × time × EtOH experience interaction (F(2, 36)=0.41; NS); EtOH experience effect (F(1, 18)=0.03; NS)).