Peripheral chemoreflex is activated during short-term sustained hypoxia (SH), and the first synapse of these afferents is located in Nucleus Tractus Solitarius (NTS). NTS neurons projecting to the ventral lateral medulla (NTS-VLM) are part of the respiratory pathways of the chemoreflex. SH increases the magnitude of basal respiratory parameters in rats from Wistar-Hannover strain. In this study, we hypothesized that the observed changes in the respiratory pattern in response to SH were due to changes in the GABAergic modulation of the synaptic transmission of NTS-VLM neurons. We used an electrophysiological approach to record the synaptic activity of NTS neurons labeled with a retrograde tracer previously microinjected into VLM of Wistar-Hannover rats submitted to 24 h SH. The data are showing that: (a) the amplitude of evoked inhibitory currents in NTS-VLM neurons of SH rats was reduced and not accompanied by any change in rise-time and decay-time; (b) the 1/CV² and the number of failures in response to evoked currents were also affected by SH; (c) the frequency of spontaneous inhibitory currents was reduced by SH without changes in amplitude and half-width. These effects of SH were observed in NTS-VLM neurons located in caudal and intermediate NTS, but not in NTS-VLM neurons located in the rostral NTS. We conclude that SH causes a reduction in inhibitory modulation onto NTS-VLM neurons by pre-synaptic mechanisms, which may contribute to the observed changes in the respiratory pattern of Wistar-Hannover rats submitted to SH.

外周化学反射在短期持续缺氧 (SH) 期间被激活，这些传入神经的第一个突触位于孤束核 (NTS)。投射到腹外侧髓质 (NTS-VLM) 的 NTS 神经元是化学反射呼吸通路的一部分。SH 增加了来自 Wistar-Hannover 菌株的大鼠的基础呼吸参数的幅度。在这项研究中，我们假设观察到的响应 SH 的呼吸模式变化是由于 NTS-VLM 神经元突触传递的 GABA 能调节的变化。我们使用电生理学方法来记录 NTS 神经元的突触活动，该神经元标记有逆行示踪剂，之前微量注射到提交 24 小时 SH 的 Wistar-Hannover 大鼠的 VLM 中。数据表明：（a）SH大鼠NTS-VLM神经元诱发抑制电流幅度降低，且不伴有上升时间和衰减时间的变化；(b) 1/CV ²并且响应诱发电流的故障次数也受 SH 的影响；(c) 自发抑制电流的频率被 SH 降低，幅度和半宽没有变化。在位于尾部和中间 NTS 的 NTS-VLM 神经元中观察到 SH 的这些影响，但在位于头侧 NTS 的 NTS-VLM 神经元中没有观察到。我们得出结论，SH 通过突触前机制导致对 NTS-VLM 神经元的抑制性调制减少，这可能有助于观察到提交给 SH 的 Wistar-Hannover 大鼠的呼吸模式的变化。