Abstract
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 Ca2+ 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 Ca2+ currents in neurons in the ventrolateral, not dorsomedial, region of the SCN were larger during early than late night, whereas L-type Ca2+ 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 Ca2+ current in retinorecipient neurons is related to the differential involvement of T-type VGCC in phase delays and advances.
| Original language | English |
|---|---|
| Pages (from-to) | 1215-1222 |
| Number of pages | 8 |
| Journal | European Journal of Neuroscience |
| Volume | 21 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 2005 Mar 1 |
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Keywords
- Electrophysiology
- Photic resetting
- Retinohypothalamic tract
- SCN
ASJC Scopus subject areas
- Neuroscience(all)
Cite this
Voltage-gated calcium channels play crucial roles in the glutamate-induced phase shifts of the rat suprachiasmatic circadian clock. / Kim, Do Young; Choi, Hee Joo; Kim, Jeong Sook; Kim, Yoon Sik; Jeong, Do Ung; Shin, Hyung Cheul; Kim, Mi Jin; Han, Hee Chul; Hong, Seung Kil; Kim, Yang In.
In: European Journal of Neuroscience, Vol. 21, No. 5, 01.03.2005, p. 1215-1222.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Voltage-gated calcium channels play crucial roles in the glutamate-induced phase shifts of the rat suprachiasmatic circadian clock
AU - Kim, Do Young
AU - Choi, Hee Joo
AU - Kim, Jeong Sook
AU - Kim, Yoon Sik
AU - Jeong, Do Ung
AU - Shin, Hyung Cheul
AU - Kim, Mi Jin
AU - Han, Hee Chul
AU - Hong, Seung Kil
AU - Kim, Yang In
PY - 2005/3/1
Y1 - 2005/3/1
N2 - 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 Ca2+ 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 Ca2+ currents in neurons in the ventrolateral, not dorsomedial, region of the SCN were larger during early than late night, whereas L-type Ca2+ 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 Ca2+ current in retinorecipient neurons is related to the differential involvement of T-type VGCC in phase delays and advances.
AB - 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 Ca2+ 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 Ca2+ currents in neurons in the ventrolateral, not dorsomedial, region of the SCN were larger during early than late night, whereas L-type Ca2+ 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 Ca2+ current in retinorecipient neurons is related to the differential involvement of T-type VGCC in phase delays and advances.
KW - Electrophysiology
KW - Photic resetting
KW - Retinohypothalamic tract
KW - SCN
UR - http://www.scopus.com/inward/record.url?scp=20244390460&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=20244390460&partnerID=8YFLogxK
U2 - 10.1111/j.1460-9568.2005.03950.x
DO - 10.1111/j.1460-9568.2005.03950.x
M3 - Article
C2 - 15813931
AN - SCOPUS:20244390460
VL - 21
SP - 1215
EP - 1222
JO - European Journal of Neuroscience
JF - European Journal of Neuroscience
SN - 0953-816X
IS - 5
ER -