Maze-learning behavior in early adrenalectomized rats.
Rats adrenalectomized (ADX) on day 11 of life display enhanced brain growth due, at least in part, to a stimulation of cell proliferation and myelinogenesis. The present study investigated some functional consequences of this treatment. Rats were ADX or sham-operated (SHAM) on postnatal day 11 and then tested in adulthood for their problem-solving ability in a Hebb-Williams maze. The mean number of errors committed by ADX rats was lower than that of the SHAM controls on every test problem of the maze. ADX subjects also left the start box more quickly and ran the maze faster than the controls. When a subset of these same subjects was tested for running wheel activity, the ADX animals showed greater baseline running behavior and also learned more readily to respond to a fixed-interval schedule of reinforcement. The remaining animals were subjected to carcass analysis, which revealed that ADX rats under the food-restricted conditions necessary for maze testing had a lower percentage of body fat and a higher relative water content than SHAMs. Although there may be some relationship between enhanced maze-learning performance and altered activity or motivation in the ADX animals, the overall results suggest that the performance of these subjects reflects a real difference in learning ability. The neural mechanisms underlying this difference remain to be elucidated.
Yehuda
R
R
Department of Psychology, University of Massachusetts, Amherst 01003.
McDonald
D
D
Heller
H
H
Meyer
J
J
D000311:Adrenal Glands / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000254:growth & development; D003345:Corticosterone / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology*; D005260:Female; D009042:Motivation / Q000502:physiology; D009043:Motor Activity / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
D003345:Corticosterone