Previous studies have found GABA in vestibular end organs. However, existence of GABA receptors or possible GABAergic effects on vestibular nerve afferents has not been investigated. The current study was conducted to determine whether activation of GABA-B receptors affects calyx afferent terminals in the central region of the cristae of semicircular canals. We used patch clamp recording in P13 - P18 Sprague-Dawley rats of either sex. Application of GABA-B receptor agonist baclofen inhibited voltage-sensitive potassium currents. This effect was blocked by selective GABA-B receptor antagonist CGP 35348. Application of antagonists of small (SK) and large (BK) conductance potassium channels almost completely blocked the effects of baclofen. The remaining baclofen effect was blocked by cadmium chloride, suggesting that it could be due to inhibition of voltage gated calcium channels. Furthermore, baclofen had no effect in the absence of calcium in the extracellular fluid. Inhibition of potassium currents by GABA-B activation resulted in an excitatory effect on calyx terminal action potential firing. While in the control condition calyces could only fire a single action potential during step depolarizations, in the presence of baclofen they fired continuously during steps and a few even showed repetitive discharge. We also found a decrease in threshold for action potential generation and a decrease in first spike latency during step depolarization. These results provide the first evidence for the presence of GABA-B receptors on calyx terminals, show that their activation results in an excitatory effect and that GABA inputs could be used to modulate calyx response properties.

中文翻译：

---

GABAB 受体的激活导致大鼠半规管嵴中花萼末端的兴奋性调节。

以前的研究已经在前庭终末器官中发现了 GABA。然而，尚未研究 GABA 受体的存在或可能对前庭神经传入的 GABA 能效应。目前的研究是为了确定 GABA-B 受体的激活是否影响半规管嵴中央区域的花萼传入末梢。我们在 P13 - P18 Sprague-Dawley 大鼠中使用了膜片钳记录。GABA-B 受体激动剂巴氯芬的应用抑制电压敏感性钾电流。这种作用被选择性 GABA-B 受体拮抗剂 CGP 35348 阻断。小 (SK) 和大 (BK) 电导钾通道拮抗剂的应用几乎完全阻止了巴氯芬的作用。剩余的巴氯芬作用被氯化镉阻断，表明这可能是由于抑制了电压门控钙通道。此外，巴氯芬在细胞外液中没有钙的情况下没有作用。GABA-B 激活对钾电流的抑制导致对花萼末端动作电位放电的兴奋作用。虽然在控制条件下，花萼在步进去极化过程中只能激发单一动作电位，但在巴氯芬存在的情况下，它们在步进过程中连续激发，一些甚至表现出重复放电。我们还发现动作电位产生的阈值降低，并且在步进去极化过程中第一次尖峰延迟降低。这些结果提供了花萼末端存在 GABA-B 受体的第一个证据，