Figure 1.

Effects of cocaine on background and burst-firing rates in ad libitum-fed and food-restricted mice. A, B, Single-unit extracellular recordings of DA neurons were established in ad libitum (A) and food-restricted (B) mice for 20 min. Cocaine (10 mg/kg, i.p.) was administered, and 5 min later recordings were resumed for a duration of 10 min. Burst events are marked by black horizontal bars. C, Summarized data indicated no difference in background firing rate between groups. However, cocaine did produce a decrease in firing rate in AL mice (indicated by red asterisk) as well as FR mice (indicated by black asterisk). D, Burst-firing analysis indicated that under control conditions neurons in food-restricted mice exhibited a greater number of bursts per minute than ad libitum mice (indicated by black asterisk on left). Cocaine significantly increased the number of bursts per minute in the food-restricted mice (indicated by black asterisk on top) but not in ad libitum mice. Ad Lib, ad libitum.