Tail-pinch-induced hyperphagia in weanling rats with dorsomedial hypothalamic lesions.
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Dorsomedial hypothalamic lesions (DMNL) were produced in 26dayold and 44dayold male rats. Shamoperated rats served as controls. Tailpinching (TP) was performed for five minutes at a time over two periods: the first TP period of six sessions each from postoperative day 1 to day 17 and the second TP period of eight sessions from postoperative day 18 to day 35. Three equicloric diets, highcarbohydrate, highfat, and highprotein, were presented ad libitum in pellet form during the TP sessions. Lab chow was available ad libitum in the home cages. Rats with DMNL at age 26 days did not show TPinduced hyperphagia and HCD preference compared to the controls until the second TP period. In rats lesioned at age 44 days, TPinduced hyperphagia and HCDpreference (compared with controls) became evident immediately after the operation. In the home cages (lab chow), DMNL rats showed a decline in food intake from the first to the second TP period, while the shamoperated controls showed an increase. TPinduced hyperphagia in the rat with DMNL does not appear to be caused by some arousalrelated process as has been shown for the rat with lateral hypothalamic lesions. Lesions in the nigrostriatal system have been reported to attenuate TPinduced feeding, while the present study indicates that lesions in the DMN enhance it. This suggests that fibers in the central nervous system may be involved in facilitation or inhibition of TPinduced eating. Copyright 1980 Alan R. Liss, Inc.
