Persistent subthreshold voltage-dependent cation single channels in suprachiasmatic nucleus neurons.
The hypothalamic suprachiasmatic nucleus (SCN) contains the primary circadian pacemaker in mammals, and transmits circadian signals by diurnal modulation of neuronal firing frequency. The ionic mechanisms underlying the circadian regulation of firing frequency are unknown, but may involve changes in membrane potential and voltage-gated ion channels. Here we describe novel tetrodotoxin- and nifedipine-resistant subthreshold, voltage-dependent cation (SVC) channels that are active at resting potential of SCN neurons and increase their open probability (P(o)) with membrane depolarization. The increased P(o) reflects changes in the kinetics of the slow component of the channel closed-time, but not the channel open-time or fast closed-time. This study provides a background for investigation of the possible role of SVC channels in regulation of circadian oscillations of membrane excitability in SCN neurons.
Kononenko
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NI
Department of Biomedical Sciences, Section of Anatomy and Neurobiology, Colorado State University, Fort Collins, CO 80523, USA.
Medina
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Dudek
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FE
D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013493:Suprachiasmatic Nucleus / Q000502:physiology*
D015220:Calcium Channels