Intermittent access to a sucrose solution for rats causes long-term increases in consumption

- Rats were given continuous or second-, third-, or fourth-day access to 4% sucrose.
- Access every fourth day led to sucrose consumption twice that of continuous access.
- When moved to alternate-day access, rats maintained differences for 24 days.
- Elevated sucrose intake reduced chow intake, and rats' weights were unaffected.
- Increased sucrose intake was due to larger sucrose meals, suggesting delayed satiety.

Intermittent access to palatable food can elevate consumption beyond an animal's immediate needs. If adult male rats (with ad lib access to food and water) are provided with a 4% sucrose solution, daily sucrose consumption is determined by the sucrose access schedule: access that is intermittent leads to high levels of consumption. In Experiment 1, sucrose solutions were first provided continuously or every second, third, or fourth day for 23.5 h over 49 days. Continuous-access sucrose consumption averaged 102 g per day, while that for access every fourth day averaged 294 g. Daily consumption averages for access every second and third day fell between these two extremes. When all rats were then given alternate-day access to sucrose for 24 days in Phase II, the previously established consumption differences were maintained. Body weight was unaffected by sucrose access; rats adjusted their food consumption so that total calorie intake remained constant. In Experiment 2, compared to continuous 4% sucrose solution access, access every third day markedly elevated daily sucrose consumption after only four sucrose exposures. With this shorter Phase I, sucrose intake in the continuous group increased markedly when in Phase II all rats were given alternate day access. In Experiment 3, a lick-by-lick analysis of the difference in sucrose consumption between access every third day and continuous access revealed that all rats were consuming a similar number of sucrose meals; however, the meals were larger both in the first hour and over the whole 24 h with intermittent access. This suggests a change in satiety as a mechanism underlying sucrose consumption difference.