Level of satiety: GABA and pentose shunt activities in three brain sites associated with feeding

The hypothesis addressed was that metabolic activity within specific brain areas may be altered to depict peripheral metabolic status. Sixty-three female Sprague-Dawley rats (225 g) received 150, 100, or 50% of normal intake by gastric intubation for 7 days. The incentive for spontaneous feeding would be inhibited in 150% fed rats (anoretic), stimulated in 50% fed rats (hungry), and maintained in 100% fed rats (control). Glucose flux through the gamma-aminobutyric acid shunt of the ventrolateral hypothalamus was 32% lower in hungry rats and 35% higher in anoretic rats relative to control values. Glucose flux through the pentose shunt of the ventromedial hypothalamus was 111% lower in hungry rats and 152% higher in anoretic rats relative to control values. Pentose shunt activity in the area postrema nucleus of the solitary tract (AP NTS) was 116% lower in hungry rats and 60% higher in anoretic rats relative to control values; however, hungry and anoretic rats had AP NTS pentose shunt activities that were not different from control values but were different from each other. The data demonstrate that within selective brain sites, specific pathways for glucose oxidation are affected by energy intake and may be used by the rat to assess and respond to changes in peripheral energy status.