Effect of beta-adrenergic antagonists on the spontaneous appetite for NaCl solution in rats

Chronic dietary administration of the beta-adrenergic antagonist, propranolol (1.6-2.0 g/kg), to both male and female rats induced an appetite for 0.25 M NaCl solution when the rats were offered a choice between distilled water and salt solution to drink. Treatment was also accompanied by a significant reduction in both water and food intakes. In addition, increases in intake of NaCl solution during treatment with propranolol were correlated significantly with increases in urinary sodium output. To test for completeness of beta-adrenergic blockade, treated and control rats in the first study were administered isoproterenol (25 micrograms/kg b.w., SC) acutely and given only water to drink. The increased 1 hr water intake characteristically accompanying acute administration of isoproterenol was blocked completely by propranolol. Additional experiments were carried out with butoxamine, a selective beta 2-adrenoceptor antagonist, (1.5 and 3.0 g/kg of food) to determine its effect on intake of 0.25 M NaCl solution. Butoxamine failed to produce a significant effect on salt appetite. The results indicate that chronic treatment with propranolol, but not butoxamine, induces an appetite for NaCl solution. They further suggest, but do not prove, that beta 1-adrenoceptors may be involved in the appetite for NaCl solutions in rats.