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Exp Neurobiol 2023; 32(2): 83-90

Published online April 30, 2023

https://doi.org/10.5607/en22040

© The Korean Society for Brain and Neural Sciences

mGluR1 Regulates the Interspike Interval Threshold for Dendritic Ca2+ Transients in the Cerebellar Purkinje Cells

Dong Cheol Jang1,2,3, Changhyeon Ryu1†, Geehoon Chung3, Sun Kwang Kim3 and Sang Jeong Kim1*

1Department of Physiology, Neuroscience Research Center, Wide River Institute of Immunology, Seoul National University College of Medicine, Seoul 03080, 2Department of Brain and Cognitive Science, College of Natural Science, Seoul National University, Seoul 08826, 3Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 02447, Korea

Correspondence to: *To whom correspondence should be addressed.
TEL: 82-2-740-8229, FAX: 82-2-763-9667
e-mail: sangjkim@snu.ac.kr
Current address: The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Received: November 7, 2022; Revised: February 24, 2023; Accepted: March 29, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Ca2++ transients can be observed in the distal dendrites of Purkinje cells (PCs) despite their lack of action potential backpropagation. These Ca2++ events in distal dendrites require specific patterns of PC firing, such as complex spikes (CS) or simple spikes (SS) of burst mode. Unlike CS, which can act directly on voltage-gated calcium channels in the dendrites through climbing fiber inputs, the condition that can produce the Ca2++ events in distal dendrites with burst mode SS is poorly understood. Here, we propose the interspike interval threshold (ISIT) for Ca2++ transients in the distal dendrites of PC. We found that to induce the Ca2++ transients in distal dendrites the frequency of spike firing of PC should reach 250 Hz (3 ms ISI). Metabotropic glutamate receptor 1 (mGluR1) activation significantly relieved the ISIT and established cellular conditions in which spike firing with 50 Hz (19 ms ISI) could induce Ca2++ transients in the distal dendrites. In contrast, blocking T-type Ca2++ channels or depleting the endoplasmic reticulum Ca2++ store resulted in a stricter condition in which spike firing with 333 Hz (2 ms ISI) was required. Our findings demonstrate that the PC has strict ISIT for dendritic Ca2++ transients, and this ISIT can be relieved by mGluR1 activation. This strict restriction of ISIT could contribute to the reduction of the signal-to-noise ratio in terms of collecting information by preventing excessive dendritic Ca2++ transients through the spontaneous activity of PC.

Graphical Abstract


Keywords: Cerebellum, Purkinje cells, Dendrites, Calcium signaling