Glycolysis selectively shapes the presynaptic action potential waveform.
Mitochondria are major suppliers of cellular energy in neurons; however, utilization of energy from glycolysis vs. mitochondrial oxidative phosphorylation (OxPhos) in the presynaptic compartment during neurotransmission is largely unknown. Using presynaptic and postsynaptic recordings from the mouse calyx of Held, we examined the effect of acute selective pharmacological inhibition of glycolysis or mitochondrial OxPhos on multiple mechanisms regulating presynaptic function. Inhibition of glycolysis via glucose depletion and iodoacetic acid (1 mM) treatment, but not mitochondrial OxPhos, rapidly altered transmission, resulting in highly variable, oscillating responses. At reduced temperature, this same treatment attenuated synaptic transmission because of a smaller and broader presynaptic action potential (AP) waveform. We show via experimental manipulation and ion channel modeling that the altered AP waveform results in smaller Ca2+influx, resulting in attenuated excitatory postsynaptic currents (EPSCs). In contrast, inhibition of mitochondria-derived ATP production via extracellular pyruvate depletion and bath-applied oligomycin (1 μM) had no significant effect on Ca2+influx and did not alter the AP waveform within the same time frame (up to 30 min), and the resultant EPSC remained unaffected. Glycolysis, but not mitochondrial OxPhos, is thus required to maintain basal synaptic transmission at the presynaptic terminal. We propose that glycolytic enzymes are closely apposed to ATP-dependent ion pumps on the presynaptic membrane. Our results indicate a novel mechanism for the effect of hypoglycemia on neurotransmission. Attenuated transmission likely results from a single presynaptic mechanism at reduced temperature: a slower, smaller AP, before and independent of any effect on synaptic vesicle release or receptor activity.
Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada.
Brendan
B
Lujan
Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Minas Gerais, Brazil; and.
Christopher
C
Kushmerick
Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, Nevada.
Tania Das
0000-0003-0671-7670
TD
Banerjee
Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, Nevada.
Ruben K
0000-0002-9946-9591
RK
Dagda
Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada; rendenr@unr.edu.
Robert
0000-0001-7905-4789
R
Renden
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D000963:Antimetabolites / Q000494:pharmacology; D001933:Brain Stem / Q000166:cytology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D003847:Deoxyglucose / Q000494:pharmacology; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005947:Glucose / Q000494:pharmacology; D006019:Glycolysis / Q000187:drug effects / Q000502:physiology*; D007210:Indoleacetic Acids / Q000494:pharmacology; D019807:Iodoacetic Acid / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects; D009840:Oligomycins / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*
D000963:Antimetabolites; D004791:Enzyme Inhibitors; D007210:Indoleacetic Acids; D008164:Luminescent Proteins; D009840:Oligomycins; C037009:1-O-indol-3-ylacetylglucose; D003847:Deoxyglucose; D005947:Glucose; D019807:Iodoacetic Acid
bioenergetics; calyx of Held; hypoglycemia; oxidative phosphorylation; stroke