Gruhn Matthias, Guckenheimer John, Land Bruce, Harris-Warrick Ronald M
Department of Integrative Physiology, University of Colorado, Boulder, USA.
J Neurophysiol. 2005 Oct;94(4):2888-900. doi: 10.1152/jn.00434.2005. Epub 2005 Jul 13.
Delayed rectifier potassium currents [I(K(V))] generate sustained, noninactivating outward currents with characteristic fast rates of activation and deactivation and play important roles in shaping spike frequency. The pyloric motor network in the stomatogastric ganglion of the spiny lobster, Panulirus interruptus, is made up of one interneuron and 13 motor neurons of five different classes. Dopamine (DA) increases the firing frequencies of the anterior burster (AB), pyloric (PY), lateral pyloric (LP), and inferior cardiac (IC) neurons and decreases the firing frequencies of the pyloric dilator (PD) and ventricular dilator (VD) neurons. In all six types of pyloric neurons, I(K(V)) is small with respect to other K(+) currents. It is made up of at least two TEA-sensitive components that show differential sensitivity to 4-aminopyridine and quinidine, and have differing thresholds of activation. One saturable component is activated at potentials above -25 mV, whereas the second component appears at more depolarized voltages and does not saturate at voltage steps up to +45 mV. The magnitude of the components varies among cell types but also shows considerable variation within a single type. A subset of PY neurons shows a marked enhancement in spike frequency with DA; DA evokes a pronounced reversible increase in I(K(V)) conductance of < or = 30% in the PY neurons studied, and on average significantly increases both components of I(K(V)). The AB neuron also shows a reversible 20% increase in the steady state I(K(V)). DA had no effect on I(K(V)) in PD, LP, VD, and IC neurons. The physiological roles of these currents and their modulation by DA are discussed.
延迟整流钾电流[I(K(V))]产生持续的、非失活的外向电流，具有快速激活和失活的特征速率，并在塑造动作电位频率中发挥重要作用。多刺龙虾（Panulirus interruptus）胃神经节中的幽门运动网络由一个中间神经元和13个不同类别的运动神经元组成。多巴胺（DA）增加前爆发神经元（AB）、幽门神经元（PY）、外侧幽门神经元（LP）和下心神经元（IC）的放电频率，并降低幽门扩张神经元（PD）和心室扩张神经元（VD）的放电频率。在所有六种类型的幽门神经元中，相对于其他K(+)电流，I(K(V))较小。它由至少两个对四乙铵敏感的成分组成，这些成分对4-氨基吡啶和奎尼丁表现出不同的敏感性，并且具有不同的激活阈值。一个可饱和成分在高于-25 mV的电位下被激活，而第二个成分出现在更去极化的电压下，并且在高达+45 mV的电压阶跃下不饱和。这些成分的大小在细胞类型之间有所不同，但在单一类型中也表现出相当大的变化。一部分PY神经元在DA作用下动作电位频率显著增加；在所研究的PY神经元中，DA引起I(K(V))电导明显可逆增加≤30%，并且平均显著增加I(K(V))的两个成分。AB神经元在稳态I(K(V))中也表现出20%的可逆增加。DA对PD、LP、VD和IC神经元的I(K(V))没有影响。本文讨论了这些电流的生理作用及其受DA的调节。
