AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 2 423-R427, Copyright © 1995 by American Physiological Society
Neuropeptide Y fails to increase intraoral intake in rats
R. J. Seeley, C. J. Payne and S. C. Woods
Department of Psychology, University of Washington, Seattle 98195.
Neuropeptide Y (NPY) has a potent orexigenic effect when administered
either into the third ventricle or directly into hypothalamic nuclei, but
the mechanism by which NPY increases intakes is poorly understood. The
present study tested the ability of NPY to increase intake of the rat in
the intraoral intake test, which focuses on the highly stereotyped
consummatory phase of ingestion by introducing a 0.1 M sucrose solution
directly into the oral cavity of rats via indwelling intraoral cannulas.
Doses of 3, 9.5, and 30 micrograms of NPY, when administered into the third
ventricle, all failed to change intraoral intake compared with a saline
control. Food deprivation (24 h), however, nearly doubled intraoral intake.
Additionally, in separate experiments, 9.5 micrograms of NPY significantly
increased both 1-h food intake and 1-h bottle intake of 0.1 M sucrose.
These results are consistent with two conclusions. 1) NPY does not affect
the consummatory phase of ingestion. 2) NPY administration does not
completely mimic the stimulus state associated with food deprivation, since
food deprivation but not NPY administration increases intake in the
intraoral intake test.
