title: The depolarizing action of GABA in cultured hippocampal neurons is not due to the absence of ketone bodies.
abstract: Two recent reports propose that the depolarizing action of GABA in the immature brain is an artifact of in vitro preparations in which glucose is the only energy source. The authors argue that this does not mimic the physiological environment because the suckling rats use ketone bodies and pyruvate as major sources of metabolic energy. Here, we show that availability of physiologically relevant levels of ketone bodies has no impact on the excitatory action of GABA in immature cultured hippocampal neurons. Addition of β-hydroxybutyrate (BHB), the primary ketone body in the neonate rat, affected neither intracellular calcium elevation nor membrane depolarizations induced by the GABA-A receptor agonist muscimol, when assessed with calcium imaging or perforated patch-clamp recording, respectively. These results confirm that the addition of ketone bodies to the extracellular environment to mimic conditions in the neonatal brain does not reverse the chloride gradient and therefore render GABA hyperpolarizing. Our data are consistent with the existence of a genuine "developmental switch" mechanism in which GABA goes from having a predominantly excitatory role in immature cells to a predominantly inhibitory one in adults.
authors: Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America. jaylyn.waddell@gmail.com
authors: Jaylyn
authors: J
authors: Waddell
authors: Jimok
authors: J
authors: Kim
authors: Bradley E
authors: BE
authors: Alger
authors: Margaret M
authors: MM
authors: McCarthy
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D006624:Hippocampus / Q000166:cytology*; D007657:Ketone Bodies / Q000172:deficiency* / Q000378:metabolism; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D007657:Ketone Bodies; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D002118:Calcium; D020155:3-Hydroxybutyric Acid