Differential Regulation of Cell Proliferation and Apoptosis by Melatonin Receptor Subtype-Signaling in the Adult Murine Brain.

Background/aims: Zeitgeber time (ZT)-dependent changes in cell proliferation and apoptosis are regulated by melatonin receptor (MT)-mediated signaling in the adult hippocampus and hypothalamic-hypophyseal system. There are two G-protein-coupled MT subtypes, MT1 and MT2. Therefore, the present study examined which MT subtype is required for the regulation of ZT-dependent changes in cell proliferation and/or apoptosis in the adult murine brain and pituitary.

Impact of melatonin receptor-signaling on Zeitgeber time-dependent changes in cell proliferation and apoptosis in the adult murine hippocampus.

The hippocampus is subjected to diurnal/circadian rhythms on both the morphological and molecular levels. Certain aspects of cell proliferation in the adult hippocampus are regulated by melatonin and accompanied by apoptosis to ensure proper tissue maintenance and function. The present study investigated Zeitgeber time (ZT)-dependent changes in cell proliferation and apoptosis in the adult murine hippocampus and their regulation by melatonin receptor type1 and type2 (MT1/2)-mediated signaling.

Impact of Melatonin on Zeitgeber Time-Dependent Changes in Cell Proliferation and Apoptosis in the Adult Murine Hypothalamic-Hypophyseal System.

Background/aims: Cell proliferation and apoptosis are known to adjust neuroendocrine circuits to the photoperiod. The latter is communicated by melatonin, the hormone secreted by the pineal organ. The present study investigated zeitgeber time (ZT)-dependent changes in cell proliferation and apoptosis in the adult murine neuroendocrine system and their regulation by melatonin.

When does it start ticking? Ontogenetic development of the mammalian circadian system.

Circadian rhythms in physiology and behavior ensure that vital functions are temporally synchronized with cyclic environmental changes. In mammals, the circadian system is conducted by a central circadian rhythm generator that resides in the hypothalamic suprachiasmatic nucleus (SCN) and controls multiple subsidiary circadian oscillators in the periphery. The molecular clockwork in SCN and peripheral oscillators consists of autoregulatory transcriptional/translational feedback loops of clock genes.

Tafa-3 encoding for a secretory peptide is expressed in the mouse pars tuberalis and is affected by melatonin 1 receptor deficiency.

The hypophysial pars tuberalis (PT) is an important interface between neuroendocrine brain centers (hypothalamus, pineal organ) and the anterior lobe of the hypophysis (PD). The best investigated role of the PT is the control of seasonally changing functions. In mammals, melatonin secreted from the pineal organ represents a major input signal to the PT.

Expression patterns of neurexin-1 and neuroligins in brain and retina of the chick embryo: Neuroligin-3 is absent in retina.

Neuroligins (NLs) constitute a family of cell-surface proteins that interact with neurexins (beta-Nxs), another class of neuronal cell-surface proteins, one of each class functioning together in synapse formation. The localization of the various neurexins and neuroligins, however, has not yet been clarified in chicken. Therefore, we studied the expression patterns of neurexin-1 (Nx-1) and neuroligin-1 and -3 during embryonic development of the chick retina and brain by reverse-transcriptase polymerase chain reaction (RT-PCR) and in situ hybridization (ISH).