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Voltage-dependent calcium channels regulate melatonin output from cultured chick pineal cells
1Laboratory of Neurophysiology, NINCDS, Bethesda, Maryland 20892.
Summary
Chick pineal cells show circadian melatonin rhythms. Voltage-dependent calcium channels regulate this rhythm, with "L-type" channels specifically involved in melatonin synthesis pathways.
Area of Science:
- Neuroscience
- Chronobiology
- Cell Biology
Background:
- Chick pineal cells exhibit a circadian rhythm in melatonin production.
- Extracellular potassium (K+) influences nocturnal melatonin release.
Purpose of the Study:
- To investigate the role of voltage-dependent calcium channels in regulating melatonin output in chick pineal cells.
- To elucidate the specific types of calcium channels involved in melatonin synthesis.
Main Methods:
- Primary culture of chick pineal cells.
- Measurement of melatonin production and release.
- Whole-cell patch-clamp electrophysiology to record calcium currents.
- Pharmacological manipulation using calcium channel blockers and activators.
Main Results:
- Divalent cations (Co2+, Cd2+, Mn2+) reduced nocturnal melatonin output.
- Nitrendipine and nifedipine inhibited the nocturnal melatonin rise, while Bay K 8644 enhanced it.
- Patch-clamp studies identified distinct transient and sustained calcium currents, both blocked by Co2+ or Cd2+.
- The sustained current, sensitive to Bay K 8644 and nifedipine, was linked to melatonin regulation.
Conclusions:
- Voltage-dependent calcium channels play a critical role in regulating melatonin output in chick pineal cells.
- "L-type" calcium channels, mediating the sustained calcium current, are implicated in the pathways controlling melatonin synthesis, independent of vesicular release.
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