Subcutaneous release of amino acid loads on food and water intake in the rat

A cellophane sac containing a mixture of amino acids was implanted under the skin of the freely fed and watered rat. After its dissolution in body fluid, the load diffused out of the sac according to an exponential function. Water intake increased maximally during the period of most rapid release of amino acids into the body. Food intake was depressed most effectively somewhat later. The anorexigenic effect of a mixture consisting solely of essential amino acids was greater than that of a mixture containing a proportion of dispensable amino acids. Effects of amino acids which facilitate the urea cycle indicated that ammonia toxicity contributed to the suppression of intake by the highest dose of essential amino acids (90 mmoles/kg). The moderate suppression of feeding by a mixture containing both essential and dispensable amino acids was potentiated by inclusion of glucose. This suggested that metabolic effects of the amino acids, other than ammonia production, contributed to the observed inhibition of feeding.