Departments of Neural and Behavioral Sciences (H.J.G., S.L.S., G.M.H.) and Anesthesiology and Perioperative Medicine (V.R.-V., P.B.H.), Penn State University College of Medicine, Hershey, Pennsylvania.
Departments of Neural and Behavioral Sciences (H.J.G., S.L.S., G.M.H.) and Anesthesiology and Perioperative Medicine (V.R.-V., P.B.H.), Penn State University College of Medicine, Hershey, Pennsylvania
Mol Pharmacol. 2024 Oct 17;106(5):253-263. doi: 10.1124/molpharm.124.000957.
The orexigenic gut peptide ghrelin is an endogenous ligand for the growth hormone secretagogue receptor type 1a (GHSR1a). Systemic ghrelin administration has previously been shown to increase gastric motility and emptying. While these effects are known to be mediated by the vagus nerve, the cellular mechanism underlying these effects remains unclear. Therefore, the purpose of the present study was to investigate the signaling mechanism by which GHSR1a inhibits voltage-gated Ca channels in isolated rat gastric vagal afferent neurons using whole-cell patch-clamp electrophysiology. The ghrelin pharmacological profile indicated that Ca currents were inhibited with a log (Ic) = -2.10 ± 0.44 and a maximal inhibition of 42.8 ± 5.0%. Exposure to the GHSR1a receptor antagonist (D-Lys3)-GHRP-6 reduced ghrelin-mediated Ca channel inhibition (29.4 ± 16.7% vs. 1.9 ± 2.5%, = 6, = 0.0064). Interestingly, we observed that activation of GHSR1a inhibited Ca currents through both voltage-dependent and voltage-independent pathways. We also treated the gastric neurons with either pertussis toxin (PTX) or YM-254890 to examine whether the Ca current inhibition was mediated by the G or G family of subunits. Treatment with both PTX (Ca current inhibition = 15.7 ± 10.6%, = 8, = 0.0327) and YM-254890 (15.2 ± 11.9%, = 8, = 0.0269) blocked ghrelin's effects on Ca currents, as compared with control neurons (34.3 ± 18.9%, = 8). These results indicate GHSR1a can couple to both G and G in gastric vagal afferent neurons. Overall, our findings suggest GHSR1a-mediated inhibition of Ca currents occurs through two distinct pathways, offering necessary insights into the cellular mechanisms underlying ghrelin's regulation of gastric vagal afferents. SIGNIFICANCE STATEMENT: This study demonstrated that in gastric vagal afferent neurons, activation of GHSR1a by ghrelin inhibits voltage-gated Ca channels through both voltage-dependent and voltage-independent signaling pathways. These results provide necessary insights into the cellular mechanism underlying ghrelin regulation of gastric vagal afferent activity, which may benefit future studies investigating ghrelin mimetics to treat gastric motility disorders.
胃泌酸调节肽 ghrelin 是生长激素促分泌素受体 1a（GHSR1a）的内源性配体。先前的研究表明，全身给予 ghrelin 可增加胃动力和排空。虽然这些作用被认为是通过迷走神经介导的，但这些作用的细胞机制尚不清楚。因此，本研究旨在使用全细胞膜片钳电生理学研究 GHSR1a 通过何种信号机制抑制分离的大鼠胃迷走传入神经元中的电压门控钙通道。ghrelin 的药理学特征表明，钙电流受到抑制，log（Ic）=-2.10±0.44，最大抑制率为 42.8±5.0%。暴露于 GHSR1a 受体拮抗剂（D-Lys3）-GHRP-6 可降低 ghrelin 介导的钙通道抑制（29.4±16.7%对 1.9±2.5%，=6，=0.0064）。有趣的是，我们观察到 GHSR1a 的激活通过电压依赖性和电压非依赖性途径抑制钙电流。我们还用百日咳毒素（PTX）或 YM-254890 处理胃神经元，以检查钙电流抑制是否由 G 或 G 亚基家族介导。PTX 处理（钙电流抑制=15.7±10.6%，=8，=0.0327）和 YM-254890 处理（15.2±11.9%，=8，=0.0269）均阻断了 ghrelin 对钙电流的作用，与对照神经元（34.3±18.9%，=8）相比。这些结果表明，GHSR1a 可在胃迷走传入神经元中与 G 和 G 偶联。总体而言，我们的研究结果表明，GHSR1a 通过两种不同的途径介导钙电流的抑制，为 ghrelin 调节胃迷走传入的细胞机制提供了必要的见解。意义声明：本研究表明，在胃迷走传入神经元中，ghrelin 通过 GHSR1a 的激活通过电压依赖性和电压非依赖性信号通路抑制电压门控钙通道。这些结果为 ghrelin 调节胃迷走传入活动的细胞机制提供了必要的见解，这可能有助于未来研究 ghrelin 类似物治疗胃动力障碍。
