Nitric oxide reduces hypophagia induced by threonine free diet in the rat

Food intake and concentrations of glutamic (GLU) and aspartic (ASP) acids in the nucleus accumbens were monitored in male Sprague-Dawley rats fed a threonine free diet. These variables were measured before and after an intracerebroventricular injection of 20 nmole nitroprusside (NP), a non-enzymatic nitric oxide donor. The same variables were also monitored in: (a) rats fed a threonine free diet and injected with saline; (b) animals fed a standard diet and injected with nitroprusside; (c) rats fed a standard diet and injected with saline. The results showed that the threonine-free diet reduced food intake and GLU and ASP concentrations in the accumbens. NP reduced the hypophagia, but it did not change GLU and ASP levels in rats fed the threonine-free diet. In animals fed the standard diet, NP increased GLU and ASP concentration, and food intake. No change was found in the animals with saline injection. These findings suggest that nitric oxide reduces the hypophagia in the rats fed a threonine-free diet. The lack of increase in GLU and ASP concentration in the nucleus accumbens of the hypophagic rats indicates that NP acts on hypophagia independently by GLU and ASP.