Analysis of polysaccharide taste in hamsters: behavioral and neural studies

A series of studies was carried out in hamsters (Mesocricetus auratus) to determine whether polysaccharides have behavioral and neurophysiological characteristics that distinguish them from simple sugars. Behavioral studies utilized solutions of glucose, maltose, sucrose, Polycose, and glycogen in two-bottle preference tests and in tests of generalization of conditioned taste aversions. Multiunit and single-unit responses of the chorda tympani nerve were studied with the same stimuli. Neural responses to Polycose and glycogen were found to be generated primarily by ionic contaminants. Dialysis or deionization dramatically reduced electrophysiological responses, a result consistent with occurrence of Polycose and glycogen sensitivity in electrolyte-sensitive nerve fibers. Effects of treatment with the Na + -channel blocker amiloride and cross-adaptation were also consistent with neural responses generated by ionic contaminants. Hamsters showed strong preferences for the sugars and Polycose, a mixture of glucose polymers with alpha-1,4 linkages, and even stronger preferences for a glycogen preparation. Conditioned flavor aversions were established to glycogen, sucrose, and maltose, but no aversion was learned to 3.2% Polycose. The learned aversion to maltose partly generalized to glycogen and sucrose, but sucrose and glycogen did not cross-generalize. Deionization did not affect the preferences for Polycose and glycogen but removal of contaminants of mol.wt. < or = 7000 Da greatly reduced preference for glycogen. In conclusion, glycogen itself, after removal of low molecular weight contaminants, is a poor taste stimulus in hamsters, both behaviorally and neurophysiologically. However, Polycose is highly preferred by hamsters but gives little chorda tympani response after removal of ionic contaminants. In alert animals, the action of salivary amylase on polysaccharides may produce simpler, detectable taste stimuli.