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Voltage‐gated calcium channels play crucial roles in the glutamate‐induced phase shifts of the rat suprachiasmatic circadian clock
Author(s) -
Kim Do Young,
Choi Hee Joo,
Kim Jeong Sook,
Kim Yoon Sik,
Jeong Do Ung,
Shin Hyung Cheul,
Kim Mi Jin,
Han HeeChul,
Hong Seung Kil,
Kim Yang In
Publication year - 2005
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2005.03950.x
Subject(s) - suprachiasmatic nucleus , neuroscience , circadian rhythm , glutamate receptor , glutamatergic , voltage dependent calcium channel , circadian clock , biology , chemistry , endocrinology , medicine , calcium , receptor
The resetting of the circadian clock based on photic cues delivered by the glutamatergic retinohypothalamic tract is an important process helping mammals to function adaptively to the daily light–dark cycle. To see if the photic resetting relies on voltage‐gated Ca 2+ channels (VGCCs), we examined the effects of VGCC blockers on the glutamate‐induced phase shifts of circadian firing activity rhythms of suprachiasmatic nucleus (SCN) neurons in hypothalamic slices. First, we found that a cocktail of amiloride, nimodipine and ω‐conotoxin MVIIC (T‐, L‐ and NPQ‐type VGCC antagonists, respectively) completely blocked both phase delays and advances, which were, respectively, induced by glutamate application in early and late night. Next, we discovered that: (i) amiloride and another T‐type VGCC antagonist, mibefradil, completely obstructed the delays without affecting the advances; (ii) nimodipine completely blocked the advances while having less impact on delays; and (iii) ω‐conotoxin MVIIC blocked largely, if not entirely, both delays and advances. Subsequent whole‐cell recordings revealed that T‐type Ca 2+ currents in neurons in the ventrolateral, not dorsomedial, region of the SCN were larger during early than late night, whereas L‐type Ca 2+ currents did not differ from early to late night in both regions. These results indicate that VGCCs play important roles in glutamate‐induced phase shifts, T‐type being more important for phase delays and L ‐type being so for phase advances. Moreover, the results point to the possibility that a nocturnal modulation of T‐type Ca 2+ current in retinorecipient neurons is related to the differential involvement of T‐type VGCC in phase delays and advances.