Energy substrate availability as a determinant of neuronal resting potential, GABA signaling and spontaneous network activity in the neonatal cortex in vitro.
While the ultimate dependence of brain function on its energy supply is evident, how basic neuronal parameters and network activity respond to energy metabolism deviations is unresolved. The resting membrane potential (E(m)) and reversal potential of GABA-induced anionic currents (E(GABA)) are among the most fundamental parameters controlling neuronal excitability. However, alterations of E(m) and E(GABA) under conditions of metabolic stress are not sufficiently documented, although it is well known that metabolic crisis may lead to neuronal hyper-excitability and aberrant neuronal network activities. In this work, we show that in slices, availability of energy substrates determines whether GABA signaling displays an inhibitory or excitatory mode, both in neonatal neocortex and hippocampus. We demonstrate that in the neonatal brain, E(m) and E(GABA) strongly depend on composition of the energy substrate pool. Complementing glucose with ketone bodies, pyruvate or lactate resulted in a significant hyperpolarization of both E(m) and E(GABA), and induced a radical shift in the mode of GABAergic synaptic transmission towards network inhibition. Generation of giant depolarizing potentials, currently regarded as the hallmark of spontaneous neonatal network activity in vitro, was strongly inhibited both in neocortex and hippocampus in the energy substrate enriched solution. Based on these results we suggest the composition of the artificial cerebrospinal fluid, which bears a closer resemblance to the in vivo energy substrate pool. Our results suggest that energy deficits induce unfavorable changes in E(m) and E(GABA), leading to neuronal hyperactivity that may initiate a cascade of pathological events.
Holmgren
Carl D
CD
INMED-INSERM U901, Université de la Méditerranée, Marseille, France.
Mukhtarov
Marat
M
Malkov
Anton E
AE
Popova
Irina Y
IY
Bregestovski
Piotr
P
Zilberter
Yuri
Y
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D020155:3-Hydroxybutyric Acid / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001639:Bicarbonates / Q000378:metabolism; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007657:Ketone Bodies / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D008954:Models, Biological; D019579:Neocortex / Q000166:cytology*; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D019289:Pyruvic Acid; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D018709:Statistics, Nonparametric; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
D001639:Bicarbonates; D018691:Excitatory Amino Acid Antagonists; D007657:Ketone Bodies; D011810:Quinoxalines; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D005680:gamma-Aminobutyric Acid; D015763:2-Amino-5-phosphonovalerate; D019289:Pyruvic Acid; D005947:Glucose; D020155:3-Hydroxybutyric Acid