Hyperphagia and obesity produced by parasagittal and coronal hypothalamic knife cuts: further evidence for a longitudinal feeding inhibitory pathway.

Hyperphagia and obesity are produced both by parasagittal knife cuts through the medial hypothalamus and by coronal knife cuts through the posterior hypothalamus. The results of this study indicate that the two types of cuts produce their overeating effect by severing the same neural pathway. Experiment 1 demonstrated that unilateral parasagittal knife cuts combined with contralateral coronal cuts in either the posterior hypothalamus or the midbrain significantly increase food intake and body weight. Experiment 2 revealed that bilateral parasagittal cuts and bilateral coronal cuts in the hypothalamus produce qualitatively similar effects on food intake, diurnal ingestive pattern, finickiness, and amphetamine anorexia. The two types of cuts differentially altered water intake, however. In Experiment 3, coronal cuts in the posterior hypothalamus, like parasagittal cuts in the medial hypothalamus, were found to increase the food intake and body weight of rats previously given bilateral parasagittal transections through the lateral perifornical region. The neuroanatomy and neurochemistry of the longitudinal feeding inhibitory pathway suggested by these results are discussed.