In:
Journal of Neurophysiology, American Physiological Society, Vol. 120, No. 3 ( 2018-09-01), p. 1264-1273
Abstract:
The current electrophysiological study investigated the functional roles of high- and low-voltage-activated Ca 2+ channel subtypes on glutamatergic small mossy fiber nerve terminals (SMFTs) that synapse onto rat hippocampal CA3 neurons. Experiments combining both the “synapse bouton” preparation and single-pulse focal stimulation technique were performed using the conventional whole cell patch configuration under voltage-clamp conditions. Nifedipine, at a high concentration, and BAY K 8644 inhibited and facilitated the glutamatergic excitatory postsynaptic currents (eEPSCs) that were evoked by 0.2-Hz stimulation, respectively. However, these drugs had no effects on spontaneous EPSCs (sEPSCs). Following the use of a high stimulation frequency of 3 Hz, however, nifedipine markedly inhibited eEPSCs at the low concentration of 0.3 µM. Moreover, ω-conotoxin GVIA and ω-agatoxin IVA significantly inhibited both sEPSCs and eEPSCs. Furthermore, SNX-482 slightly inhibited eEPSCs. R(−)-efonidipine had no effects on either sEPSCs or eEPSCs. It was concluded that glutamate release from SMFTs depends largely on Ca 2+ entry through N- and P/Q-type Ca 2+ channels and, to a lesser extent, on R-type Ca 2+ channels. The contribution of L-type Ca 2+ channels to eEPSCs was small at low-firing SMFTs but more significant at high-firing SMFTs. T-type Ca 2+ channels did not appear to be involved in neurotransmission at SMFTs. NEW & NOTEWORTHY Action potential-evoked glutamate release from small mossy fiber nerve terminals (SMFTs) that synapse onto rat hippocampal CA3 neurons is regulated by high-threshold but not low-threshold Ca 2+ channel subtypes. The functional contribution mainly depends on N- and P/Q-type Ca 2+ channels and, to a lesser extent, on R-type Ca 2+ channels. However, in SMFTs stimulated at a high 3-Hz frequency, L-type Ca 2+ channels contributed significantly to the currents. The present results are consistent with previous findings from fluorometric studies of large mossy fiber boutons.
Type of Medium:
Online Resource
ISSN:
0022-3077
,
1522-1598
DOI:
10.1152/jn.00571.2017
RVK:
XA 10000 ; XA 552555
Language:
English
Publisher:
American Physiological Society
Publication Date:
2018
detail.hit.zdb_id:
80161-6
detail.hit.zdb_id:
1467889-5
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