Schedule dependence of schedule induced polydipsia and lever pressing

Abstract

Two male hooded rats maintained at 80% of initial body weight were tested for schedule induced polydipsia at fixed time (FT) intervals of 1.0, 2.0, 3.0, 4.0 and 5.0 min. A total of 180 45 mg pellets were delivered during the test session. Each animal was tested five times at each FT interval. Total number of licks, lever presses and water consumption increased as the FT interval was increased to a maximum at 4.0 min and then decreased at 5.0 min. Although delivery of the food pellet was not contingent upon pressing the lever, lever pressing occurred and followed the same time related function as licking and water consumption. Results were interpreted in terms of increased motor activity attributed to intermittent food delivery.