Sustained hypoxia (SH) changes the glutamatergic transmission in Nucleus Tractus Solitarius (nTS) neurons of mice

Neuronal activity in the nTS is critical for cardiorespiratory regulation and can be influenced by interaction with astrocytes via glutamate transporters (GLT-1 and GLAST). Conditions such as SH alter cardiorespiratory function in mice. We hypothesize that SH increases the glutamatergic transmission in the nTS neurons, in part via altered neuron-astrocyte interaction via glutamate uptake through GLT-1 and/or GLAST. nTS brainstem slices were obtained from C57Bl/6j mice after normoxia (N, FiO 2 =0.21, 24h) or SH (FiO 2 =0.10, 24h). Electrophysiological properties of neurons were evaluated using whole-cell patch-clamp (single cell) and Multi-Electrode Array (MEA, extracellular discharge). The contribution of astrocyte glutamate transporters was examined in presence of Dihydrokainic acid (DHK; 300 μM) to block GLT-1 and (3S)-3-[[3-[[4-(trifluoromethyl)benzoyl]amino]phenyl] methoxy]-l-aspartic acid (TFB-TBOA; 500 nM) to block GLT-1 and GLAST. SH increased AMPA [N:-65±9pA(n=42) vs SH:-95±9pA(n=48)] and NMDA currents [N:35±7pA(n=12) vs SH:72±15pA(n=10)] evoked by solitary tract (TS) stimulation in nTS neurons, suggesting enhanced excitatory transmission. Across the entire nTS, SH elevated spontaneous extracellular activity [N:14±0.9(n=246) vs SH:24±1(n=461)]. We subsequently evaluated if this SH-mediated elevation of activity was related to changes in neuron-astrocyte interaction or postsynaptic parameters. SH did not alter the neuron-astrocyte interaction, GTL-1 inhibition comparably elevated AMPA current evoked by TS stimulation in neurons of the normoxia [aCSF:-88±23pA/pF(n=12) vs aCSF+DHK:-139±46pA/pF(n=7)] and SH group [aCSF:-70±15pA/pF(n=7) vs aCSF+DHK:-141±32pA/pF(n=7)]. In addition, the depolarization of membrane potential, holding current and single cell AP by DHK were comparable between N and SH. We also evaluated the number of events in neurons after DHK and TFB-TBOA in the MEA protocol. DHK increased number of events in normoxia [aCSF:14±1 vs aCSF+DHK:24±2(n=246)] and SH [aCSF:24.3±1 vs aCSF+DHK:38±1(n=461)], the same were observed with TFB-TBOA in normoxia [aCSF:14±1 vs aCSF+TFB-TBOA:31±2] and SH neurons [aCSF:24±1 vs aCSF+TFB-TBOA:64±2(n=461)]. Finally, SH increased postsynaptic AMPA [N:-11±2pA(n=14) vs SH:-17±2pA(n=16)] and NMDA current in neurons [N:6±1pA(n=14) vs SH:15±2pA(n=13)]. In summary, our data demonstrate that SH increases excitatory transmission, spontaneous extracellular activity and postsynaptic parameters, but does not modify neuron-astrocyte interaction. Together, the observed change in the glutamatergic transmission and spontaneous extracellular activity in nTS neurons promoted by SH is problably related to elevated postsynaptic currents rather than altered neuron-astrocyte interactions. CAPES (#88887.635569/2021-00), FAPESP (#2018/15957-2), CNPq (#309338/2020-4) and NIH (HL166183). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.