Nocturnal cyclic versus continuous total parenteral nutrition: Food intake and feeding pattern in rats

Abstract

Total parenteral nutrition (TPN), providing the equivalent of 100% of mean daily oral intake for 24 hours, depressed spontaneous food intake (SFI) in rats by a mean >80%. Whether TPN had the same effect on SFI when given either in 12-hour cycles (Cyclic-TPN) or in 24 hours (Continuous-TPN) for 8 days was tested in 16 rats with jugular catheters, placed in metabolic cages modified with an Automated Computerized Rat Eater Meter. This continuously measures food intake and its dependent indexes: meal number, meal size, meal duration, meal sniffs and intermeal sniffs. Both rat groups ate the same amounts of chow before TPN. On starting TPN, food intake decreased by >80% in Cyclic-TPN and >50% in Continuous-TPN during each first infusion period. A nadir in food intake was reached in 48 hours with Cyclic-TPN and in 72 hours with Continuous-TPN. Thereafter, there was no food intake during the 12 hours of Cyclic-TPN, with minimal food intake during the intervening 12 hours of non-TPN normal saline infusion period. In both forms of TPN infusion, a reduction in food intake was achieved by a reduction in meal number and size, and thus in meal duration. Feeding-related sniffing activity was decreased by similar amounts with Cyclic- or Continuous-TPN. Cyclic-TPN for 12 hours had no advantage over Continuous-TPN, in that there was no compensatory enhancement of food intake and meal-related behavior during the cyclic non-TPN normal saline period.