Figure 3.

Adult acquisition of nicotine self-administration, same subjects (n = 45) as in Fig. 2. (a) Over the first 20 days, nicotine was self-administered in increasing amounts via active lever presses (***days: P < 0.001), (b) unaccompanied by growth in inactive lever pressing. Neonatal ventral hippocampal lesions (NVHL) rats showed stronger acquisition (in terms of overall active lever pressing (***lesion: P < 0.001) and shape of the acquisition curve (**lesion × days: P < 0.01), while not differing from SHAMS on inactive lever pressing. Significance levels of post hoc one-way ANOVAs on each day by lesion status are denoted directly above error bars (*P < 0.05; **P < 0.01; ***P < 0.001). (c) NVHLs increased active lever time-out responding (**P < 0.01) but not (d) time out-inactive lever pressing. Over acquisition, (e) NVHL rats achieved nicotine acquisition (20 days of ≥ 20 infusions/day) earlier than SHAMS (**P < 0.01), accumulating (f) greater total nicotine intake (**P < 0.01). Adolescent nicotine exposure (NIC groups) did not produce differential effects on these measures compared to adolescent saline exposure. Data depicted as means ± SEM