AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 6 1242-R1247, Copyright © 1993 by American Physiological Society
Rapid-onset "need-free" sodium appetite after lesions of the dorsomedial medulla
G. L. Edwards, T. G. Beltz, J. D. Power and A. K. Johnson
Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens 30602.
Previous studies indicate the dorsomedial hindbrain is important in the
maintenance of fluid balance. Lesions centering on the area postrema (AP)
result in enhanced ad libitum intake of concentrated saline solutions on a
24-h basis as well as enhanced excretion of water and electrolytes.
Additionally, rats with lesions of the AP are reported to have an
exaggerated behavioral response to dipsogenic challenges that mimic
depletion of the extracellular fluid compartment. In the studies reported
here, we have observed that rats with lesions of the AP and immediately
adjacent nucleus of the solitary tract consume large quantities of
concentrated saline solutions within minutes of presentation. This intake
does not appear to be related to sodium loss or depletion because the
lesioned rats are in a positive sodium balance and the appetite persists
after bilateral nephrectomy. These data, in conjunction with earlier
studies, suggest that the dorsomedial medulla, including the AP, acts to
prevent overconsumption of water and sodium that could result in increased
extracellular fluid volume.
