Figure 5.

The figure illustrates data obtained from the 10-min pre-session blackout periods. Mean operant and head-entry responses (and standard errors) for the experimental group, per training and testing conditions, are depicted. Significant differences, based on a paired-t test, were only evident for the last two days of training. An effect of nicotine sensitization is apparent in the comparison of the first two administrations of nicotine (i.e. Block 1) versus the last two days (Block 6) for both operant and head-entry responses. For operant responses, some contextual control was exerted by the nicotine context during the test, but there was great variability in the degree to which the context controlled operant responding during the pre-session blackout.