Abstract
Daily temporal patterns from cellular activities to animal behaviors are governed by the endogenous clock system, which has been proposed to be driven by gene transcription-translation feedback loops. The circadian oscillations in the clock genes have been observed in a wide range of systems, from unicellular organisms to mammalian cells and from peripheral organs to the central nervous system. Cytosolic free Ca2+ is a general intracellular messenger that regulates diverse cellular processes, including membrane potentials, secretions and gene expressions, and is involved in a generation of various biological rhythms. Our recent studies in neurons playing a critical role for circadian locomotor rhythms in mammals and fruit flies demonstrated Ca2+ oscillations with a circadian (c.a. 24 h) period. In mice, hypothalamic suprachiasmatic nucleus (SCN) neurons, which are known as circadian pacemakers, display autonomous clock gene oscillations, cytosolic Ca2+ oscillations, action potential firing rhythms, and secretion rhythms in circadian fashion. In fruit flies, a larval circadian clock may be located within peripheral endocrine organs, such as the corpus allatum (CA) and prothoracic gland (PG), where display robust circadian rhythms in nuclear Per protein levels, even in the in vitro cultures up to for a week. In adult flies, the circadian rhythm is more evident in the specific cerebral neurons, the ventral lateral neurons (LNvs) which receive visual inputs from the compound eyes. The recent technical breakthroughs to visualize these cellular rhythms will be discussed in the present presentation. [J Physiol Sci. 2007;57 Suppl:S63]
