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Neuronal Synchronization and Ionic Mechanisms for Propagation of Excitation in the Functional Network of Immortalized GT1–7 Neurons: Optical Imaging with a Voltage‐Sensitive Dye
Author(s) -
Hiruma Hiromi,
Uemura Tsuguo,
Kimura Fukuko
Publication year - 1997
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.1997.00645.x
Subject(s) - apamin , channel blocker , tetraethylammonium , chemistry , voltage gated ion channel , biophysics , patch clamp , voltage dependent calcium channel , endocrinology , medicine , neuroscience , electrophysiology , ion channel , potassium channel , biology , receptor , calcium , biochemistry , organic chemistry , potassium
Immortalized gonadotropin releasing hormone (GnRH) neurons (GT1 cell line) in culture release GnRH in a pulsatile manner, suggesting that GT1 cells form a functional neuronal network. Optical imaging techniques and a voltage‐sensitive fluorescent dye (RH795) were used to study the mechanism of neuronal synchronization and intercellular communication in cultured GT1–7 cells (one of the subclones of the GT1 cell line). The majority (79%) of GT1–7 cells in contact with one another revealed synchronized fluctuations in spontaneous neuronal activity. When a cell in contact with other cells was electrically stimulated, the evoked excitation was propagated to neighbouring cells. The ionic mechanisms involved in the propagation of electrical signals between interconnected GT1–7 cells were investigated using various blockers of Na + , Ca 2+ and K + channels. The propagation of stimulus‐evoked excitation was prevented by the voltage‐dependent Na + channel blocker tetrodotoxin. It was also prevented by the voltage‐dependent Ca 2+ channel blockers, Ni + (nonselective), nimodipine (L‐type) and flunarizine (T‐type>L‐type), but not apparently affected by & ohgr;‐agatoxin IVA (P‐ and Q‐type) and & ohgr;‐conotoxin MVIIA (N‐type). The propagation was not influenced by the K + channel blockers, quinine, tetraethylammonium and Ba 2+ , but in some cases, it was enhanced by 4‐aminopyridine (4‐AP) and prevented by apamin. These results suggest that voltage‐dependent Na + channels and L‐ and T‐type Ca 2+ channels are involved in the propagation of electrical signals in the GT1–7 neuronal network. Ionic mechanisms, through 4‐AP‐ or apamin‐sensitive K + channels, also seem to be involved in the regulation of signal propagation. These mechanisms may underlie the functioning of the neuronal network formed by immortalized GnRH neurons.