Glycolysis regulates neuronal excitability via lactate receptor, HCA1R

Abstract

Repetitively firing neurons during seizures accelerate glycolysis to meet energy demand, which leads to the accumulation of extracellular glycolytic by-product lactate. Here, we demonstrate that lactate rapidly modulates neuronal excitability in times of metabolic stress via the hydroxycarboxylic acid receptor type 1 (HCA1R) to modify seizure activity. The extracellular lactate concentration, measured by a biosensor, rose quickly during brief and prolonged seizures. In two epilepsy models, mice lacking HCA1R (lactate receptor) were more susceptible to developing seizures. Moreover, HCA1R deficient (knock out, KO) mice developed longer and more severe seizures than wild-type littermates (WT). Lactate perfusion decreased neuronal tonic and phasic activity of CA1 pyramidal neurons in GCAMP7 imaging experiments. HCA1R agonist, 3Cl-HBA, reduced the activity of CA1 neurons in HCA1R WT but not in KO mice. In patch-clamp recordings, both lactate and 3CL-HBA hyperpolarized CA1 pyramidal neurons. HCA1R activation reduced the spontaneous EPSC frequency and altered the paired-pulse ratio of evoked EPSCs in HCA1R WT but not in KO mice, suggesting it diminished presynaptic release of excitatory neurotransmitters. Overall, our studies demonstrate that excessive neuronal activity accelerates glycolysis to generate lactate, which translocates to the extracellular space to slow neuronal firing and inhibit excitatory transmission via HCA1R. These studies may identify novel anticonvulsant target and seizure termination mechanisms.

Glycolytic lactate production supports status epilepticus in experimental animals

“…Pre‐ and post‐calibration was performed for each biosensor probe, that is, the rising concentration of the analyte of interest (D‐glucose for a glucose biosensor probe and L‐lactate for a lactate biosensor probe), injection of the interference solution (ascorbic acid) followed by a final injection of the analyte. Animals were subjected to seizure and SE induction protocols, as described previously 28 . Animals were monitored by continuous video‐EEG with simultaneous lactate or glucose concentration measurements until the end of the seizures and SE.…”

“…The end of SE was defined as a decline in spike–wave discharge frequency below 1 Hz. We scored behavioral seizures using a modified Racine scale 29 as previously described 28,30,31 …”

“…We used a mix of pENN.AAV.CamKII 0.4.Cre.SV40 and pGP‐AAV‐syn‐FLEX‐jGCaMP7s‐WPRE (Addgene, viral titer 1 × 10 13 vg/mL) viruses to study calcium dynamics in vitro. The virus was injected as described previously 28,31 . Briefly, p30‐40 C57Bl/6 mice were stereotaxically injected with a mix of viruses in the ratio 1:1 bilaterally in the ventral and dorsal CA1 (anteroposterior, −2.54; mediolateral, ∓2.00; dorsoventral, −1.20, and AP, −3.40; ML, ∓3.35; DV, −2.25).…”

“…Lactate or glucose concentration during a single seizure and SE was measured using a lactate oxidase-based and a glucose oxidase-based biosensor probe (Pinnacle Technologies, KS, USA) with simultaneous video-EEG monitoring. 28 We designed the recording assembly composed of an intracranial guide cannula (biosensor insertion) with an attached hippocampal recording electrode. The assembly consisted of a cortical electrode ipsilateral, a reference electrode, and a bipolar-insulated stainless-steel stimulating electrode contralateral to the probe.…”

“…We scored behavioral seizures using a modified Racine scale 29 as previously described. 28,30,31 Immunohistochemistry and imaging Animals were perfused transcardially with 4% paraformaldehyde (PFA) in 0.1 M phosphate buffer (PB). The brains were harvested and postfixed in 4% PFA solution overnight and cryoprotected in 30% sucrose for 48 h. Immunohistochemistry was performed as previously described.…”