The effect of removing area postrema on the sodium and potassium balances and consumptions in the rat.

Previous studies have indicated that rats lose weight and develop a taste preference for solutions of sodium chloride after area postrema has been removed; results in other species have suggested that area postrema may be concerned with regulating the excretion of sodium and potassium. The results reported here demonstrate that in rats the reduction of weight can be explained adequately by anorexia, that diminished excretion of sodium and potassium results from anorexia, and that the consequent slower rate of gain of weight causes diminution of sodium and potassium balances. The results also show that the rats do not drink more of a solution of sodium chloride because they eat less, and conversely that when they can drink a saline solution they do not eat more: and that they do not drink more saline because of salt loss. Furthermore, individual rats show no significant correlation between the severity of anorexia, and the increased consumption of saline. Taken together the results suggest that primary disorder of regulation of intake occurs in rats after area postrema has been removed, and that the reduced intake of food and the increased intake of sodium chloride occur independently.