Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil.
Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, Brazil.
J Neuroendocrinol. 2021 May;33(5):e12977. doi: 10.1111/jne.12977. Epub 2021 May 4.
A neural circuit between the paraventricular nucleus of the hypothalamus (PVN) and the dorsal motor nucleus of the vagus (DMNV) constitutes part of an important parasympathetic autonomic pathway that controls hepatic glucose production. Intracerebroventricular injection of insulin activates oxytocinergic neurones in the PVN and elicits the release of oxytocin into the circulation, which plays an important role in the metabolism of glucose. Moreover, the central action of insulin can reduce the concentration of glucose in blood taken from the hepatic vein of Wistar rats via activation of vagal efferent nerves to the liver. This mechanism is impaired in sedentary spontaneously hypertensive rats (SHR). Because aerobic exercise increases vagal tone, partly mediated by increasing the oxytocinergic connections between the PVN and DMNV, we hypothesised that oxytocin (OT) might alter the excitability of liver-projecting DMNV neurones. Thus, we investigated the effects of OT on electrical properties of the liver-projecting DMNV neurones from Wistar, SHR subjected to 4 weeks of exercise training, as well sedentary controls, using whole cell patch-clamping. The results show that OT increased the resting membrane potential of DMNV neurones in Wistar rats, as well as the firing frequency of these cells, but not in sedentary SHR. However, in SHR subjected to 4 weeks of exercise training, the effects of OT on liver-projecting DMNV neurones of were similar to those seen in Wistar rats. These findings show that OT elicits similar changes in the electrophysiological properties of liver-projecting DMNV neurones of Wistar and exercise-trained but not sedentary SHR. These results indicate that exercise training can restore the sensitivity of liver-projecting DMNV neurones of exercise-trained SHR to OT.
下丘脑室旁核（PVN）和迷走神经背核（DMNV）之间的神经回路构成了控制肝葡萄糖产生的重要副交感自主神经通路的一部分。脑室内注射胰岛素可激活 PVN 中的催产素能神经元，并引发催产素释放到循环中，这在葡萄糖代谢中起着重要作用。此外，胰岛素的中枢作用可以通过激活迷走传出神经来减少从 Wistar 大鼠肝静脉中取出的血液中的葡萄糖浓度。这种机制在久坐的自发性高血压大鼠（SHR）中受损。由于有氧运动通过增加 PVN 和 DMNV 之间的催产素能连接来增加迷走神经张力，我们假设催产素（OT）可能改变投射到肝脏的 DMNV 神经元的兴奋性。因此，我们使用全细胞膜片钳技术研究了 OT 对来自 Wistar、接受 4 周运动训练的 SHR 以及久坐对照的投射到肝脏的 DMNV 神经元的电特性的影响。结果表明，OT 增加了 Wistar 大鼠 DMNV 神经元的静息膜电位和这些细胞的放电频率，但在久坐的 SHR 中没有增加。然而，在接受 4 周运动训练的 SHR 中，OT 对投射到肝脏的 DMNV 神经元的作用与 Wistar 大鼠相似。这些发现表明，OT 可引起 Wistar 和运动训练但不是久坐的 SHR 投射到肝脏的 DMNV 神经元的电生理特性发生相似的变化。这些结果表明，运动训练可以恢复运动训练的 SHR 投射到肝脏的 DMNV 神经元对 OT 的敏感性。
