Metabolic mapping of functional activity in rat brain and pituitary after water deprivation

Glucose utilization in rat brain and pituitary was measured in control and water-deprived rats by autoradiographic assessment of the metabolic trapping of radioactivity from [1-14C]glucose. Two days of water deprivation resulted in significant increases in hematocrit, plasma osmolality and vasopressin levels, indicating a functional activation of magnocellular vasopressin neurons. The uptake and retention of radioactivity from [1-14C]glucose in the dehydrated rats, compared to controls, was 103% greater in the magnocellular portion of the paraventricular nucleus and 74% greater in the supraoptic nucleus. Water deprivation also resulted in significant increases in glucose utilization (30-40%) in the lateral and anterior hypothalamic areas, somatosensory cortex and cingulate cortex. No change in glucose utilization after 2 days of water deprivation was apparent in the parvocellular paraventricular nucleus, periventricular nucleus of the hypothalamus, corpus callosum, organum vasculosum of the lamina terminalis (OVLT) or the subfornical organ (SFO). In the pituitary, glucose utilization was increased in the neural lobe but was unchanged in the anterior and intermediate lobes after water deprivation. Under the conditions of the present study, no increase in metabolic activity was apparent in 2 brain regions thought to be possible sources of osmoreception, the OVLT and SFO. These results do not support, but do not exclude, functional involvement of the OVLT and SFO in regulating the activity of magnocellular neurons of the paraventricular nucleus and supraoptic nucleus during chronic water deprivation.