Figure 4.

Acquisition of the instrumental response for saccharin and cocaine. (a) Rats displayed no difference in the acquisition of the instrumental response for cocaine (COC, light diamonds) or saccharin (SACC, dark circles) in the discrete-trial choice procedure. In this test, rats pressed a lever to self-administer cocaine and turned a wheel to gain access to saccharin. (b) Moreover, they learned how to earn maximal quantity of saccharin as their intake (gray circles) progressively increased.