POLYDIPSIA INDUCED BY INTERMITTENT DELIVERY OF SALTED LIQUID FOODS

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Abstract
Food‐deprived rats given constant access to water were exposed to fixed‐time presentations of soybean milk and diluted sweetened condensed cows' milk. In some conditions these liquid foods were adulterated with varying amounts of sodium chloride. Under a fixed‐time 30‐sec schedule of food delivery, little water was consumed when the food was soybean milk alone, or soybean milk with sodium chloride added in concentrations of .9, 1.8, or 3.6%. However, schedule‐induced polydipsia appeared when soybean milk adulterated with 7.2 or 14.4% sodium chloride was delivered under this schedule. When soybean milk containing 7.2% sodium chloride was presented under fixed‐time 15‐, 30‐, 60‐, 120‐, and 240‐sec schedules, schedule‐induced drinking increased with the fixed‐time value from 15 to 120 seconds, and decreased at 240 seconds. Like soybean milk, diluted sweetened condensed milk delivered under fixed‐time schedules of 30, 60, and 120 seconds failed to evoke schedule‐induced polydipsia, but did so when adulterated with 7.2% sodium chloride. Drinking induced by salted liquid foods resembled the polydipsia engendered by spaced dry‐food presentations in several ways, including temporal relation to food delivery, persistence within and across sections, sensitivity to interfood interval, and magnitude relative to intake evoked by bulk‐food presentation.