Alterations in extracellular GABA in the ventral hypothalamus of rats in response to acute glucoprivation

Abstract

gamma-Aminobutyric acidergic (GABA) mechanisms in the ventral hypothalamus may be involved in counterregulatory responses to glucoprivic episodes. Microdialysis probes (1 mm) were placed into the ventromedial hypothalamus (VMH) or lateral hypothalamus (LHA) of male Sprague-Dawley rats 3.5 h before 2-deoxy-D-glucose (2-DG) administration (200 mg/kg i.v.). Probes were perfused (2 ml/min) with Ringer solution, and samples were collected every 10 min from 30 min before to 60 min after 2-DG. By 30 min after 2-DG, GABA concentration in VMH dialysate increased in a bimodal fashion to 204 +/- 36% (P < 0.01) of baseline, and GABA concentration in LHA dialysate decreased to 77 +/- 4% (P < 0.01) of baseline. The changes in dialysate GABA concentrations occurred concurrently with the animals eating and returned to baseline by 60 min. When animals were denied access to food after 2-DG, the decrease in LHA GABA was not apparent and VMH GABA remained approximately 15% above baseline at the end of the sample period. The results of the present study provide evidence that GABAergic systems in the ventral hypothalamus are responsive to alterations in glucose status.