γ‐Aminobutyric acidB receptors and the development of the ventromedial nucleus of the hypothalamus

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Abstract
γ‐Aminobutyric acid (GABA) is a highly abundant neurotransmitter in the brain and the ligand for GABAA, GABAB, and GABAC receptors. Unlike GABAA and GABAC receptors, which are chloride channels, GABAB receptors are G‐protein linked and alter cell‐signaling pathways. Electrophysiological studies have found GABAB receptors in cultured embryonic hypothalamus, but the distribution of these receptors remains unknown. In the present study, we examined the expression of GABAB receptors in the ventromedial nucleus of the hypothalamus (VMH) during embryonic mouse development. GABAB receptors were present in the VMH at all ages examined, from embryonic day 13 to postnatal day 6. Using a brain slice preparation, we examined the effect of GABAB receptor activation on cell movement in the embryonic VMH as the nucleus forms in vitro. The GABAB receptor agonist baclofen decreased the rate of cell movement in a dose‐dependent manner. Baclofen reduced cell movement by up to 56% compared with vehicle‐treated controls. The percentage of cells moving per field and the angles of cell movement were not affected. With our previous findings of GABAA receptor activation, it is likely that GABA influences VMH development via multiple mechanisms. J. Comp. Neurol. 449:270–280, 2002.