Electric Studies of Excitation, Secretion & Contraction

描述（申请人提供）：松果体是大脑中的内分泌器官，主要受交感神经系统释放的去甲肾上腺素调节。它是我们生物钟系统的一部分，向全身传播夜间激素——褪黑激素。松果体细胞的夜间状态伴随着相对于白天状态的基因表达的广泛变化。除了哺乳动物松果体细胞不光敏外，许多表达的基因是由姐妹谱系光感受器表达的。我们的总体假设是松果体细胞在两种非常不同的电生理兴奋性之间切换

DESCRIPTION (provided by applicant): The pineal gland is an endocrine organ in the brain that is primarily regulated by noradrenaline released by the sympathetic nervous system. It is the part of our circadian clock system that broadcasts the night hormone, melatonin, to all of the body. The night state of pinealocytes is accompanied by extensive changes in gene expression relative to the day state. Many expressed genes are those expressed by a sister lineage, photoreceptors, except that mammalian pinealocytes are not photosensitive. Our overall hypothesis is that pinealocytes switch between two very different electrophysiological excitability states that contribute to regulated secretion of melatonin and to entrainment and maintenance of circadian rhythms. Using biophysical techniques, the night and day states of cultured rat pinealocytes will be contrasted in terms of their ion channel complement, calcium signal dynamics, receptor activation, second messenger levels, and secretory mechanisms. The state changes will be achieved by preincubating cultured primary cells in appropriate neurotransmitters. Cells will be dissociated from rat pineal glands, placed in cell culture, treate with norepinephrine to mimic night, and studied under the microscope with techniques such as whole-cell gigaseal recording, photometry of calcium-sensitive dyes, amperometry and HPLC of neurotransmitters, and use of various live-cell indicators for second messengers. Night pinealocytes are hypothesized to have electrical excitability related to that of photoreceptors, and day pinealocytes are hypothesized to be relatively quiescent. The hypothesis that serotonin is secreted from pinealocytes by quantal exocytosis whereas melatonin and N-acetyl serotonin are secreted by hydrophobic diffusion will also be tested. Understanding the rhythmic secretory mechanisms of the pineal will make an important contribution towards treating sleep disorders, seasonal affective responses to short days, and loss of attention due to jet lag and shift work.