FIGURE 2.

Rats with intermittent access to sugar release DA in response to drinking sucrose for 60 minutes on day 21. DA, as measured by in vivo microdialysis, increases for the daily intermittent sucrose and chow rats (open circles) on days 1, 2, and 21; in contrast, DA release was attenuated on day 21 in 3 control groups as follows: a group that only had 1-hour access to sucrose on days 1 and 21 with ad libitum chow in the interim (sucrose twice, filled circles), ad libitum sucrose and chow group (filled squares), and the daily intermittent chow group (bottom panel). The bar on the ordinate indicates the hour (0–60 min) that sucrose or chow was available for the tests. *P < 0.05.²⁹