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. 2017 Jul 26;37(30):7198–7208. doi: 10.1523/JNEUROSCI.0990-17.2017

Figure 4.

Figure 4.

After animals learned to self-administer cocaine, they learned to self-administer cocaine in accordance with an IntA schedule. Both STs (n = 19) and GTs (n = 17) escalated cocaine intake over 14 IntA sessions, with STs having consumed a greater amount of cocaine across IntA training (a). Over 14 sessions, the difference between responses to the active port in the presence of the DS+ and the DS− (filled symbols in b) increased at the same rate in STs and GTs. The difference between inactive responses in the presence of the DS+ and the DS− remained near zero over sessions (open symbols in b; note that, for calculating these differences, the number of responses during the 25 min DS− periods was divided by 5 to match the 5 min DS+ periods). By the end of IntA training (session #14), STs and GTs' cocaine consumption did not differ (c). d shows, for each block of session #14, the percentage active and inactive responses for the DS+ periods relative to the DS− periods (resp, responses; act, active, inact, inactive; mean ± SEM). During DS+ periods, responses to the active, but not inactive, port were 500–2000% over DS− periods, indicating that both STs and GTS effectively discriminated between the DS+ (drug available) and DS− (no-drug available) periods (note that, for the calculation of the data in d, DS− responses of zero were replaced by one).