AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 6 1093-R1095, Copyright © 1990 by American Physiological Society
Obese and lean Zucker rats differ in preferences for sham-fed corn oil or sucrose
D. Greenberg and S. C. Weatherford
Department of Psychiatry, Cornell University Medical College, New York.
Obese Zucker rats show greater preference for fatty foods in dietary
selection studies than do lean rats. We wished to evaluate the preference
for dietary fats in Zucker rats in the absence of postingestive cues.
Zucker rats (6 lean and 6 obese) were fitted with gastric cannulas for sham
feeding. All sham-feeding tests lasted for 30 min. On training days, rats
were sham fed 100% corn oil or, on alternate days, rats were sham fed
various concentrations of sucrose in volumes yoked to intakes of corn oil.
On preference test days, rats were offered 100% corn oil and one sucrose
concentration simultaneously for sham feeding. During preference tests,
obese rats preferred 100% corn oil to 10% sucrose, whereas lean rats
preferred 10% sucrose to 100% corn oil. Obese rats equally preferred 17.5%
sucrose and 100% corn oil, whereas lean Zucker rats equally preferred 2.5%
sucrose and 100% corn oil. When sucrose concentration was increased to 20%
both obese and lean Zucker rats preferred sucrose to 100% corn oil. These
results combined with our previously reported results showing that
intraduodenally administered fats do not differ in satiating potency for
obese and lean Zucker rats (6) strongly suggest that the preference of
obese rats for fatty foods is largely mediated by orosensory mechanisms.
