Melatonin is a neurotransmitter that modulates various physiological phenomena including regulation and maintenance of the circadian rhythm. Nicotinic acetylcholine receptors (nAChRs) play an important role in oral functions including orofacial muscle contraction, salivary secretion, and tooth development. However, knowledge regarding physiological crosstalk between melatonin and nAChRs is limited. In the present study, the melatoninmediated modulation of nAChR functions using bovine adrenal chromaffin cells, a representative model for the study of nAChRs, was investigated. Melatonin inhibited the nicotinic agonist dimethylphenylpiperazinium (DMPP) iodide-induced cytosolic free Ca2+ concentration ([Ca2+]i) increase and norepinephrine secretion in a concentrationdependent manner. The inhibitory effect of melatonin on the DMPP-induced [Ca2+]i increase was observed when the melatonin treatment was performed simultaneously with DMPP. The results indicate that melatonin inhibits nAChR functions in both peripheral and central nervous systems.

Introduction
 Materials and Methods
  1. Materials
  2. Chromaffin cell preparation
  3. Measurement of [3H]norepinephrine secretion
  4. Free Ca2+ concentration measurement
  5. Data analysis
 Results
 Discussion
 References

• Su-Hyun Jo(Department of Physiology, Institute of Bioscience and Biotechnology, BK21 Plus Graduate Program, Kangwon National University School of Medicine)
• Seung-Hyun Lee(Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry)
• Kyong-Tai Kim(Department of Life Sciences, Division of Integrative Bioscience and Biotechnology, Pohang University of Science and Technology)
• Se-Young Choi(Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry) Correspondence to