Circadian waves of cytosolic calcium concentration and long-range network connections in rat suprachiasmatic nucleus

• Published in: The European journal of neuroscience Vol. 35; no. 9; pp. 1417 - 1425
• Main Authors: Hong, Jin Hee, Jeong, Byeongha, Min, Cheol Hong, Lee, Kyoung J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.05.2012
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Axons; Calcium; Calcium - metabolism; Calcium signalling; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; Cell culture; circadian oscillation; Circadian Rhythm - physiology; Circadian rhythms; clock cell networks; CLOCK protein; Cytosol - metabolism; Dose-Response Relationship, Drug; Image Processing, Computer-Assisted; Magnetic Resonance Spectroscopy; Nervous system; Neural networks; Neural Pathways - drug effects; Neural Pathways - physiology; Organ Culture Techniques; phase waves and synchronization; Rats; Rats, Sprague-Dawley; Sodium Channel Blockers - pharmacology; Suprachiasmatic nucleus; Suprachiasmatic Nucleus - cytology; Suprachiasmatic Nucleus - drug effects; Suprachiasmatic Nucleus - physiology; suprachiasmatic nucleus calcium dynamics; Tetrodotoxin; Tetrodotoxin - pharmacology; Time Factors; Transfection
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/j.1460-9568.2012.08069.x

The suprachiasmatic nucleus (SCN) is the master clock in mammals governing the daily physiological and behavioral rhythms. It is composed of thousands of clock cells with their own intrinsic periods varying over a wide range (20–28 h). Despite this heterogeneity, an intact SCN maintains a coherent 24 h periodic rhythm through some cell‐to‐cell coupling mechanisms. This study examined how the clock cells are connected to each other and how their phases are organized in space by monitoring the cytosolic free calcium ion concentration ([Ca2+]c) of clock cells using the calcium‐binding fluorescent protein, cameleon. Extensive analysis of 18 different organotypic slice cultures of the SCN showed that the SCN calcium dynamics is coordinated by phase‐synchronizing networks of long‐range neurites as well as by diffusively propagating phase waves. The networks appear quite extensive and far‐reaching, and the clock cells connected by them exhibit heterogeneous responses in their amplitudes and periods of oscillation to tetrodotoxin treatments. Taken together, our study suggests that the network of long‐range cellular connectivity has an important role for the SCN in achieving its phase and period coherence. The suprachiasmatic nucleus (SCN) is the master clock in mammals governing the daily physiological and behavioral rhythms. It is composed of thousands of clock cells with their own intrinsic periods varying over a wide range (20∼28 h).