Figure 1:

Pretreatment with nicotine significantly increases intravenous self-administration of remifentanil. Rats were trained in 2-h sessions for five days on an FR-1 schedule of reinforcement to press a retractable lever in standard operant chambers for IVSA of RMF before being moved to an FR-2 schedule for the remaining four days. (A) Rats treated with nicotine, relative to those treated with saline, made significantly more active lever presses on days 6-9 of training. There were no differences between groups on inactive lever presses. (B) As a result, nicotine pretreatment resulted in significantly more earned RMF infusions on day five of acquisition training. *s indicate significant group differences (P < 0.05).