AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 3 658-R661, Copyright © 1990 by American Physiological Society
Accelerated gastric emptying in VMH-lesioned rats is secondary to excess weight gain
R. M. Black, K. L. Conover and H. P. Weingarten
Department of Psychology, McMaster University, Hamilton, Ontario, Canada.
This experiment evaluates the hypothesis that an accelerated rate of
gastric emptying accounts for the hyperphagia and obesity after lesions of
the ventromedial hypothalamus (VMH). Gastric emptying was measured for 16
days after the production of VMH lesions in rats maintained either ad
libitum or on restricted eating. Only ad libitum VMH-lesioned rats
demonstrated faster than normal rates of emptying. However, VMH rats
maintained at control weights showed normal rates of gastric emptying and,
even in ad libitum rats, accelerated emptying was not apparent immediately
after lesions. These findings indicate that changes of emptying are not a
primary effect of VMH lesions but that this dysfunction develops
secondarily as a consequence of excess eating and weight gain. Measurement
of stomach secretions demonstrated, however, that VMH lesions did result in
an immediate and direct effect on gastric secretion. These findings
mitigate the importance of gastric emptying in the etiology of the VMH
syndrome. Other data consistent with this conclusion are reviewed.
