NEURAL ACTIVITY AND MEAL-ASSOCIATED DRINKING IN RATS

Rats were allowed to eat a meal (chow or cracker) of approximately nor mal spontaneous size either with or without water available. They were then sacrificed for measurement of either plasma renin activity (PRA) and gut contents at the end of the meal or Fos-immunoreactivity (FLI) in brain 1 h after the meal. PRA was doubled at the end of the meal r elative to unfed controls, and this coincided with translocation of fl uid into the gut. The supraoptic acid magnocellular paraventricular nu clei showed meal-related FLI. The intensity of the FLI was related to meal size, and was less prominent in rats eating moist food. This stud y shows that normal-sized meals produce detectable changes in fluid pa rameters and activate brain locations known to be related to primary s timuli of drinking.