Grooming behavior in mice induced by stimuli of corn oil in oral cavity

Mice show a strong preference for corn oil, which was thought to be elicited by stimulation in the oral cavity. Grooming behavior is known to be induced by dopamine D(1) stimulation in rodents. Therefore, we evaluated stimulation by corn oil in the oral cavity and the contribution of D(1) receptors to corn-oil-induced grooming in mice. Intraoral injection (0.1 ml) of corn oil induced grooming behavior similarly to SKF 38393 (10 mg/kg i.p.), a D(1) agonist, and both were antagonized by pretreatment with SCH 23390, a D(1) antagonist. However, a higher dose was needed for antagonism of the corn-oil-induced grooming compared with that induced by SKF 38393. Long-chain fatty acids, their methyl esters and alcohol, their triglycerides, mineral oil and silicone oil but not glycerin, a short-chain triglyceride, xanthan gum solution, or sucrose solution also induced grooming in mice. Xanthan gum solution, which was suggested to mask oil-like texture, attenuated the silicone-oil- but not corn-oil-induced grooming when injected intraorally as a mixture with an equal volume of the oil (50% suspension). The silicone-oil-induced grooming was reduced by SCH 23390 similarly to that induced by corn oil. These results suggested that stimulation by the oil-like texture in the oral cavity in mice induced grooming behavior and that it might be mediated at least partially via D(1) receptors. Moreover, stimuli other than texture might also contribute to the corn-oil-induced grooming.