Figure 7.

Instrumental extinction, drug prime and cue-induced reinstatement tests. After 36 days of IntA self-administration all rats first underwent one day of extinction training, and then on the next day, further extinction before testing for drug-induced reinstatement of cocaine seeking behavior. Panel a shows that on the first day of extinction training both STs (n=20) and GTs (n=25) rapidly decreased instrumental responding (the number of active nose pokes), and there were no group differences in the rate of instrumental extinction (see Ahrens et al., 2015 for a comparison of Pavlovian vs. instrumental extinction in STs and GTs). Panel b shows the effect of three successive doses of cocaine, separated by 30 min, on responding, under extinction conditions. The values for the dose of 0 are the means ± SEMs for the 30-min immediately prior to the priming injections. The priming injections dose-dependently increased active responses, relative to inactive responses, and although there appears to be a group difference after the highest dose, this was not statistically significant. Panel c shows active responses on each of the 5 days of further extinction training following the drug-induced reinstatement test (n=19 STs, 23GTs). Again, there were no group differences in instrumental extinction. Panel d shows the results of the cue reinstatement test, when responding now resulted in presentation of the cue previously paired with cocaine delivery during self-administration sessions, but no cocaine was delivered. The black bars show responding at the end of extinction training and the white bars the number of active responses during the 2-hour reinstatement test. The dashed lines within the white bars indicate the mean number of inactive responses during the reinstatement test. It is clear that the cue was a highly effective conditioned reinforcer, reinstating high levels of responding, in both STs and GTs, which did not differ. Values represent means ± SEMs.