抄録
A pineal body is neurosecretory organ secreting melatonin in the night, but the characteristic and the details of the secretion control remain unclear due to small size of the principal cell (pinealocyte). In this study, whole-cell patch-electrodes were applied to pinealocytes of the rodents (ddy mouse, Wistar rat), and the characteristics of the receptors mediating autonomic neural control were analyzed. Block preparations of about 200-micron thickness were made from the pineal gland isolated from the animal, and various drugs were applied rapidly to the pinealocyte using the Y-tube method. The results show; 1. The nicotinic ACh receptors are expressed in the pinealocyte, causing membrane depolarization in response to application of nicotine. 2. The magnitude of nACh-mediated responses increased significantly during the development of the animal. The nicotinic response of the pineal gland showed obvious inward rectification, while no inter-cellular couplings were detected causing undesired space clamp condition. 3. During application of muscarine to the pinealocyte, inward currents with slow rise time and oscillatory changes in the amplitude were evoked in the cell, which recovered in several minutes after the wash out of muscarine. It is concluded that both nicotinic and muscarinic receptors are expressed in the pinealocyte, which may influence cellular metabolism of the pinealocytes leading changes in melatonin secretion. Supported by grant from Smoking Research Foundation (Japan) [J Physiol Sci. 2008;58 Suppl:S82]
