A cationic channel regulated by a vertebrate intrinsic circadian oscillator.
Secretory cells of the chicken pineal gland exhibit light-sensitive circadian rhythms in melatonin release that persist in vitro. Melatonin secretion is positively regulated by cyclic AMP and intracellular Ca2+ (refs 8, 10-15). Cyclic AMP analogues are more effective at stimulating melatonin secretion during the circadian night owing in part to increased Ca2+ influx at those times. However, this cannot be attributed to increased activity of L-type Ca2+ channels. Here we describe an unusual 40-pS cationic channel (ILOT) in cultured chicken pineal cells that is permeable to Ca2+ and active in the night but not during the day. ILOT is not voltage- or stretch-activated, it has a characteristically long open time, and its gating persists in excised inside-out patches in the absence of Ca2+ or cyclic nucleotides. Daily rhythms in ILOT gating are also observed in previously entrained chicken pineal cells free-running under constant dark conditions. Nighttime ILOT activity is not suppressed by brief light pulses.
D'Souza
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Program in Neuroscience, Department of Biological Science, Florida State University, Tallahassee 3206-4075, USA.
Dryer
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D000818:Animals; D002118:Calcium / Q000378:metabolism; D002412:Cations; D002478:Cells, Cultured; D002645:Chickens; D002940:Circadian Rhythm; D000242:Cyclic AMP / Q000378:metabolism; D003624:Darkness; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism* / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D008550:Melatonin / Q000096:biosynthesis; D008564:Membrane Potentials; D010870:Pineal Gland / Q000166:cytology / Q000378:metabolism
D002412:Cations; D007473:Ion Channels; D000242:Cyclic AMP; D008550:Melatonin; D002118:Calcium