The United Graduate School of Veterinary Science, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2012 Mar;198(3):229-37. doi: 10.1007/s00359-011-0703-0. Epub 2011 Dec 8.
It has been hypothesized that chick accessory lobes (ALs) contain functional neurons and act as a sensory organ of equilibrium. It was reported that neurons located in an outer layer of ALs showed γ-aminobutyric acid (GABA)- and glutamic acid decarboxylase (GAD)-like immunoreactivity more strongly than centrally located neurons, which were surrounded by the GAD-immunoreactive terminals. We investigated effects of GABA on the electrical activity of AL neurons. About 50% of embryonic AL neurons exhibited spontaneous firing. In the on-cell recording, GABA, muscimol, and GABA in combination with CGP35348 inhibited this firing. In whole-cell voltage clamp recordings, GABA and muscimol evoked a transient current. The mean reversal potential of GABA-evoked currents was close to the theoretical reversal potential of Cl⁻. These results indicate that GABA exerts the inhibitory effect on the firing through the activation of GABA(A) receptors. In addition, the intracellular concentration of Cl⁻ was estimated to be about 16 mM in measurements with the gramicidin-perforated configuration, indicating the physiological reversal potential of the GABA current was about -60 mV. In conclusion, AL neurons have an intrinsic mechanism to evoke the spontaneous firing, which can be arrested by the inhibitory mechanism through the activation of the GABA(A) receptors.
有人假设鸡的副腺（AL）含有功能性神经元，并作为平衡的感觉器官。据报道，位于 AL 外层的神经元比位于中央的神经元表现出更强的γ-氨基丁酸（GABA）和谷氨酸脱羧酶（GAD）样免疫反应性，而中央的神经元被 GAD 免疫反应性末端包围。我们研究了 GABA 对 AL 神经元电活动的影响。约 50%的胚胎 AL 神经元表现出自发放电。在细胞膜片钳记录中，GABA、muscimol 和 GABA 与 CGP35348 联合抑制了这种放电。在全细胞膜片钳记录中，GABA 和 muscimol 诱发了一个短暂的电流。GABA 诱发电流的平均反转电位接近 Cl⁻的理论反转电位。这些结果表明，GABA 通过激活 GABA(A)受体对放电产生抑制作用。此外，用 gramicidin 穿孔构型进行测量时，估计细胞内 Cl⁻的浓度约为 16mM，表明 GABA 电流的生理反转电位约为-60mV。综上所述，AL 神经元具有内在机制来引发自发放电，这种放电可以通过激活 GABA(A)受体的抑制机制来阻止。
