Mechanisms for enhanced feeding in the cold in rats

The effect of environmental cold upon feeding, food-motivated behavior, and gastric clearance of food was studied in rats. Rats ate liquid diet in either a 5 degrees C or 22 degrees C ambient temperature (TA) following (a) 24-hr food deprivation at TA of either 5 or 22 degrees C, or (b) 0- or 48-hr food deprivation at TA 22 degrees C. Rats ate more at 5 degrees C than at 22 degrees C regardless of the ambient temperature during deprivation. Rats increased feeding in the cold by increasing meal frequency but not meal size. Cold (5 degrees C) TA also enhanced the urge to eat. Rats bar pressed for food more often in the cold TA on a variable interval 30-sec schedule when gastric clearance of food was prevented by a pyloric noose and when food cleared from the stomach normally. Also, quinine adulteration of food suppressed food intake only in the 22 degrees C TA. Cold (5 degrees C) TA enhanced gastric clearance of liquid food within 20 min of ingestion. These results support the view that the peripheral sensation of cold is an adequate stimulus for feeding and that cold TA can stimulate feeding directly by increasing the urge to eat and indirectly, secondary to increased gastric clearance.