Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Box 951763, Los Angeles, CA 90095-1763, USA.
J Physiol. 2010 Nov 15;588(Pt 22):4431-9. doi: 10.1113/jphysiol.2010.194209. Epub 2010 Sep 20.
Since protein kinase-dependent modulation of motoneuronal excitability contributes to adaptive changes in breathing, we hypothesized that cGMP-dependent pathways activating protein kinase G (PKG) modulate motoneuronal inspiratory drive currents and long-term plasticity. In a medullary slice preparation from neonatal rat (postnatal days 0-4) generating spontaneous respiratory-related rhythm, hypoglossal (XII) motoneuronal inspiratory drive currents and respiratory-related XII nerve activity were recorded. Focal application of a PKG activator, 8-bromoguanosine-3',5'-cyclomonophosphate (8-Br-cGMP), to voltage-clamped XII motoneurones decreased inspiratory drive currents. In the presence of tetrodotoxin (TTX), 8-Br-cGMP decreased the exogenous postsynaptic inward currents induced by focal application of AMPA. Intracellular dialysis of XII motoneurones with an inhibitory peptide to PKG (PKGI) increased endogenous inspiratory-drive currents and exogenous AMPA-induced currents. Application of 8-Br-cGMP with PKGI had no further effect on spontaneous or evoked currents, confirming that the observed effects were induced by PKG. However, PKG differentially increased longer-term plasticity. Three 3 min applications (separated by 5 min) of the α(1)-adrenergic agonist phenylephrine (PE) in combination with 8-Br-cGMP yielded greater in vitro long-term facilitation than PE alone. These data indicate the presence of a cGMP/PKG-dependent signalling pathway in XII motoneurones that modulates inspiratory drive currents and plasticity of XII motoneurones, possibly contributing to their adaptation during physiological challenges, such as sleep and exercise.
由于蛋白激酶依赖性调制运动神经元兴奋性有助于呼吸的适应性变化，我们假设 cGMP 依赖性途径激活蛋白激酶 G（PKG）调制运动神经元吸气驱动电流和长期可塑性。在产生自发性呼吸相关节律的新生大鼠（出生后 0-4 天）延髓切片制备中，记录舌下神经（XII）运动神经元吸气驱动电流和呼吸相关 XII 神经活动。PKG 激活剂 8-溴鸟苷-3'，5'-环单磷酸（8-Br-cGMP）的焦点应用于电压钳制 XII 运动神经元，降低吸气驱动电流。在河豚毒素（TTX）存在下，8-Br-cGMP 降低了由 AMPA 焦点应用诱导的外生性突触后内向电流。用 PKG（PKGI）的抑制性肽对内侧 XII 运动神经元进行细胞内透析，增加了内源性吸气驱动电流和外源性 AMPA 诱导的电流。应用 8-Br-cGMP 与 PKGI 对自发或诱发电流没有进一步的影响，证实观察到的效应是由 PKG 诱导的。然而，PKG 对长期可塑性的影响不同。三种 3 分钟应用（间隔 5 分钟）的 α（1）-肾上腺素能激动剂苯肾上腺素（PE）与 8-Br-cGMP 联合应用，比单独使用 PE 产生更大的体外长期易化作用。这些数据表明，在 XII 运动神经元中存在一种 cGMP/PKG 依赖性信号通路，该通路调制吸气驱动电流和 XII 运动神经元的可塑性，可能有助于它们在生理挑战（如睡眠和运动）期间的适应。
