Electrophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council (CONICET)), Scientific Research Commission of the Province of Buenos Aires (CIC-PBA) and National University of La Plata (UNLP), Calle 526 S/N entre 10 y 11, 1900 La Plata, Buenos Aires, Argentina.
Mol Neurobiol. 2020 Feb;57(2):722-735. doi: 10.1007/s12035-019-01738-y. Epub 2019 Aug 29.
The mechanisms by which ghrelin controls electrical activity in the hypothalamus are not fully understood. One unexplored target of ghrelin is Ca3, responsible for transient calcium currents (T-currents) that control neuronal firing. We investigated the effect of ghrelin on Ca3 subtypes and how this modulation impacts on neuronal activity. We performed whole-cell patch-clamp recordings in primary mouse hypothalamic cultures to explore the effect of ghrelin on T-currents. We also recorded calcium currents from transiently transfected tsA201 cells to study the sensitivity of each Ca3 subtype to GHSR activation. Finally, we ran a computational model combining the well-known reduction of potassium current by ghrelin with the Ca3 biophysical parameter modifications induced by ghrelin to predict the impact on neuronal electrical behavior. We found that ghrelin inhibits native NiCl sensitive current currents in hypothalamic neurons. We determined that Ca3.3 is the only Ca3 subtype sensitive to ghrelin. The modulation of Ca3.3 by ghrelin comprises a reduction in maximum conductance, a shift to hyperpolarized voltages of the I-V and steady-state inactivation curves, and an acceleration of activation and inactivation kinetics. Our model-based prediction indicates that the inhibition of Ca3.3 would attenuate the stimulation of firing originating from the inhibition of potassium currents by ghrelin. In summary, we discovered a new target of ghrelin in neurons: the Ca3.3. This mechanism would imply a negative feed-forward regulation of the neuronal activation exerted by ghrelin. Our work expands the knowledge of the wide range of actions of GHSR, a receptor potentially targeted by therapeutics for several diseases.
Ghrelin 控制下丘脑电活动的机制尚未完全阐明。Ghrelin 尚未探索的一个靶点是 Ca3，它负责控制神经元放电的瞬时钙电流 (T-currents)。我们研究了 ghrelin 对 Ca3 亚型的影响，以及这种调节如何影响神经元活动。我们在原代小鼠下丘脑培养物中进行全细胞膜片钳记录，以研究 ghrelin 对 T-电流的影响。我们还从瞬时转染的 tsA201 细胞中记录钙电流，以研究每种 Ca3 亚型对 GHSR 激活的敏感性。最后，我们运行了一个计算模型，将 ghrelin 已知的钾电流减少与 ghrelin 诱导的 Ca3 生物物理参数修改相结合，以预测对神经元电行为的影响。我们发现 ghrelin 抑制下丘脑神经元中的天然 NiCl 敏感电流。我们确定 Ca3.3 是唯一对 ghrelin 敏感的 Ca3 亚型。Ghrelin 对 Ca3.3 的调节包括最大电导降低、I-V 和稳态失活曲线的超极化电压移位以及激活和失活动力学的加速。我们基于模型的预测表明，Ca3.3 的抑制将减弱 ghrelin 抑制钾电流引起的放电刺激。总之，我们在神经元中发现了 ghrelin 的一个新靶点：Ca3.3。这种机制将意味着 ghrelin 对神经元激活的负反馈调节。我们的工作扩展了 GHSR 广泛作用的知识，GHSR 是一种潜在的治疗多种疾病的靶点受体。
