Hydrogen peroxide increases GABAergic mIPSC through presynaptic release of calcium from IP₃ receptor‐sensitive stores in spinal cord substantia gelatinosa neurons

Abstract

GABAergic interneurons of the spinal cord substantia gelatinosa regulate the transmission of nociceptive information. Hydrogen peroxide (H2O2) is likely a diffusible messenger contributing to the development of long-lasting pathological pain states after nerve injury. In this study, we examined the presynaptic effects of H2O2 on the inhibitory interneurons of mouse substantia gelatinosa (SG) using whole-cell patch-clamp recordings from spinal cord slices. H2O2 increased the frequency of GABAergic miniature inhibitory postsynaptic current (mIPSC) in a concentration-dependent (10-1000 microM) manner. The profound increase in mIPSC frequency was diminished by thapsigargin or cyclopiazonic acid suggesting that the intracellular stored pool was the source of presynaptic calcium. Further examination revealed the 2-aminoethoxydiphenil borate blockable inositol-(1,4,5) trisphosphate receptor (IP3R) regulated pool of stored calcium as the likely source. The phospholipase C (PLC) blocker, 1-(6-[([17beta]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione (U73122), did not block the frequency increase, which suggested that the site of action of H2O2 lies downstream in the IP3 signalling pathway, and nifedipine-sensitivity of the frequency increase indicated a possible role of calcium-induced calcium-release. However, a direct examination of L-type voltage-gated calcium channels (VGCC) demonstrated that H2O2 did not increase the calcium influx through these channels. The H2O2 effect on mIPSC frequency was markedly reduced in the opisthotonus (Opt) mutant mice with a known deletion in the IP3R1 gene. We demonstrated that H2O2 increased presynaptic activity in the GABAergic interneurons by the release of calcium from the IP3R-regulated intracellular pool. The presynaptic IP3R could emerge as a novel target for preventing H2O2-induced synaptic plasticity in substantia gelatinosa leading to pathological pain states.

p38 mitogen-activated protein kinase independent SB203580 block of H2O2-induced increase in GABAergic mIPSC amplitude

“…The main presynaptic effect of H 2 O 2 in SG neurons is due to a presynaptic release of inositol-trisphosphate receptor-sensitive stored Ca 2+ [8]. This work reports on an atypical pharmacology exhibited by the p38 MAPK inhibitor SB203580, which blocks the postsynaptic effect of H 2 O 2 on the amplitude of mIPSCs.…”

“…SG neurons and a whole-cell patch-clamp recording were established as described [8]. The solution filling the pipette contained (in mM): 110 CsSO 4 , 0.5 CaCl 2 , 2 MgCl 2 , 5 TEACl, 5 ethylene glycol-bis (b-aminoethyl ether), 5 Mg adenosine triphosphatase, 5 N-2-hydroxyl piperazine-N′-2-ethane sulfonic acid, 270−290 mOsm/kg, pH 7.4.…”

Modulation of Presynaptic GABA Release by Oxidative Stress in Mechanically-isolated Rat Cerebral Cortical Neurons

“…In addition, H2O2 stimulated glutamate release, elevation of [Ca 2＋ ]c and ROS generation, which in turn led to neuronal cell death in cultured cortical cells [30]. A recent report demonstrated that H2O2 increased GABAergic mIPSCs through presynaptic release of Ca 2＋ from inositol-1,4,5-trisphosphate receptor-sensitive Ca 2＋ stores in the spinal cord substantia gelatinosa neurons [22]. In addition, several reports have demonstrated that cAMP-dependent PKA has an important role in certain conditions showing an increase in presynaptic GABA release in many neuronal preparations [31][32][33].…”

“…The results indicate that the amount of GABA released from presynaptic terminals might be increased by H2O2, not through activation or inhibition of PKA, but through other mechanisms. From the results of a recent report [22], it can be suggested that the potentiating effect of H2O2 on the amount of GABA released from presynaptic terminals might be through IP3-induced presynaptic Ca 2＋ increase. From the present study, it can be suggested that increased intracellular ROS of the neuronal nerve terminals of cerebral cortical neurons may increase the frequency and amount of GABA release from the presynaptic terminals and then inhibits the postsynaptic neuronal activity via increased GABAergic inhibitory synaptic transmission.…”

“…For GABAergic neurotransmission, ROS have been shown to increase release and decrease uptake of GABA in a variety of neuronal preparations [12,20,21]. A recent study indicated that H2O2 increased GABAergic mIPSCs through presynaptic inositol-1,4,5-trisphosphate receptor (IP3R)-sensitive Ca 2＋ release mechanism [22]. However, it is not clear whether cAMP-dependent protein kinase A is involved in the effect of ROS on GABAergic mIPSCs in central neurons.…”