Interaction between orosensory and postingestional stimulation in the control of corn oil intake by rats

The microstructure of the ingestive behavior of rats ingesting corn oil emulsions was analyzed to describe quantitatively how postingestional stimulation interacts with orosensory stimulation to control the intake of corn oil. Seventeen hour food deprived rats were given 30-min access intake tests with corn oil emulsions ranging in concentration from 0.125% to 64%. The volume ingested showed an inverted U shaped function over this concentration range. The Weibull function fitted to the rate of licking function showed that the initial rate of licking was an increasing linear function of the log of the concentration of corn oil. The slope of the licking rate function was an increasing curvilinear function of the log of corn oil concentration. Together these results indicate that the negative feedback effect of corn oil in the gastrointestinal tract increases more rapidly at the higher concentrations of corn oil than does its orosensory stimulating effect resulting in a decrease in the volume ingested. Unlike carbohydrates, where the increase in the initial rate of licking is a result of an increase in the size of the clusters, the increase with concentration in the initial rate of ingesting corn oil was caused by an increase in the number of clusters rather than their size. This study provides a quantitative analysis of the interaction between orosensory and postingestional stimulation, two variables that play an important role in the control of ingestion of corn oil.