Corn oil and mineral oil stimulate sham feeding in rats.

To determine the orosensory effects of oils on ingestion, we measured the 1-bottle intake of corn oil and of mineral oil during 30 minutes of sham feeding in rats that were food deprived overnight or nondeprived. Rats sham fed both oils. Food-deprived rats ingested significantly more of both oils than nondeprived rats. Rats discriminated corn oil from mineral oil and as little as 0.78% corn oil emulsion from water. When rats sham fed 8 dilutions of corn oil, intake was an inverted-U function of concentration with maximal intakes produced by 12.5%, 25% and 50% corn oil emulsions. Despite similar, sometimes equal, intakes of corn oil and mineral oil in 1-bottle tests, food-deprived and nondeprived rats showed a strong preference for corn oil in 2-bottle, sham-feeding, preference tests. The sensory mechanisms that mediate the oral effects of oil on intake and preference are not known, but the olfactory and trigeminal sensory systems are the most likely candidates. Further work is required to characterize the potency, sensitivity, and discriminability of the orosensory effects of oils, the mechanisms that mediate them, and their role in the control of fat intake.