Bilateral electrolytic lesions in the ventral midbrain tegmental nucleus of male 260 g Sprague Dawley rats produced hyperphagia with a greater than 50% increase in food intake when fed a 6% casein basal diet or a threonine basal amino acid diet (balanced amino acid diet with threonine as the most limiting amino acid for growth). However, hyperphagic rats with tegmental lesions reduced their food intake drastically as compared to the intact controls when fed the threonine imbalanced or threonine devoid diet. These animals regained their hyperphagia after re-feeding with the 6% casein basal diet but again exhibited marked food intake depression and slower adaptation when fed a high protein diet (75% casein). The ventral noradrenergic bundle has been known to traverse through the ventral tegmental nucleus. The destruction or damage of this nucleus, although raising the food intake of balanced amino acid diets, did not prevent the food intake depression of rats fed diets containing imbalanced or deficient amino acid mixtures or balanced amino acid mixtures present in excess. Thus, neither the ventral tegmental nucleus nor the noradrenergic food intake inhibitory system appears to mediate the inhibition of food intake of rats fed diets containing disproportionate amounts of amino acids. Lesions placed in areas anterior to the ventral tegmental areas produced varying degress of temporary aphagia for up to 12 days when rats were fed the 6% casein diet, but normal eating was resumed with the 6% casein or the threonine basal amino acid diet. These animals showed food intake depression similar to that of the intact controls when fed the threonine imbalanced or devoid diet. Refeeding the 6% casein diet produced normal feeding once again. However, they curtailed their food intake drastically, as did the intact controls, when fed the 75% casein diet. Present results indicate that neural fibers that are reported to course through the above mentioned neural areas are not important in mediating the control of food intake of rats fed disproportionate quantities of dietary amino acids.
- Amino acids
- Food intake
- Ventral tegmental nucleus lesions
ASJC Scopus subject areas
- Experimental and Cognitive Psychology
- Behavioral Neuroscience