体膜电位和KV1通道在皮层的轴索侧支和突触前终扣控制电位复极化

J Neurosci 2011 Oct;31(43):15490-8. [IF:7.271]

Somatic membrane potential and kv1 channels control spike repolarization in cortical axon collaterals and presynaptic boutons.

Foust AJ , Yu Y , Popovic M , Zecevic D , McCormick DA .

Departments of Neurobiology, Kavli Institute for Neuroscience, and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510, and Center for Computational Systems Biology, Fudan University, Shanghai, People's Republic of China 200433.

上海复旦大学计算系统生物学中心，康涅狄格州纽黑文科维理神经科学研究所，耶鲁大学医学院细胞和分子生理学系

Abstract

The shape of action potentials invading presynaptic terminals, which can vary significantly from spike waveforms recorded at the soma, may critically influence the probability of synaptic neurotransmitter release. Revealing the conductances that determine spike shape in presynaptic boutons is important for understanding how changes in the electrochemical context in which a spike is generated, such as subthreshold depolarization spreading from the soma, can modulate synaptic strength. Utilizing recent improvements in the signal-to-noise ratio of voltage-sensitive dye imaging in mouse brain slices, we demonstrate that intracortical axon collaterals and en passant presynaptic terminals of layer 5 pyramidal cells exhibit a high density of Kv1 subunit-containing ion channels, which generate a slowly inactivating K(+) current critically important for spike repolarization in these compartments. Blockade of the current by low doses of 4-aminopyridine or α-dendrotoxin dramatically slows the falling phase of action potentials in axon collaterals and presynaptic boutons. Furthermore, subthreshold depolarization of the soma broadened action potentials in collaterals bearing presynaptic boutons, an effect abolished by blocking Kv1 channels with α-dendrotoxin. These results indicate that action potential-induced synaptic transmission may operate through a mix of analog-digital transmission owing to the properties of Kv1 channels in axon collaterals and presynaptic boutons.