Christopher S. Colwell

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The mammalian suprachiasmatic nucleus (SCN) is a master circadian pacemaker. It is not known which SCN neurons are autonomous pacemakers or how they synchronize their daily firing rhythms to coordinate circadian behavior. Vasoactive intestinal polypeptide (VIP) and the VIP receptor VPAC(2) (encoded by the gene Vipr2) may mediate rhythms in individual SCN(More)
Neurons in the suprachiasmatic nucleus (SCN) are responsible for the generation of circadian oscillations, and understanding how these neurons communicate to form a functional circuit is a critical issue. The neurotransmitter GABA and its receptors are widely expressed in the SCN where they mediate cell-to-cell communication. Previous studies have raised(More)
The related neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are expressed at high levels in the neurons of the suprachiasmatic nucleus (SCN), but their function in the regulation of circadian rhythms is unknown. To study the role of these peptides on the circadian system in vivo, a new mouse model was developed in(More)
Endogenous processes referred to as circadian oscillators generate many of the daily rhythms in physiology and behavior of a variety of animals including humans. We investigated the possible circadian regulation of acquisition, recall and extinction in two strains of mice (C-57/6J and C-3H). Mice were trained in either the day or night with a tone and(More)
The goal of this study is to investigate the effect of the hormone melatonin on long-term potentiation and excitability measured by stimulating the Schaffer collaterals and recording the field excitatory postsynaptic potential from the CA1 dendritic layer in hippocampal brain slices from mice. Application of melatonin produced a concentration-dependent(More)
There is reason to believe that resting free calcium concentration [Ca2+]i in neurons in the suprachiasmatic nucleus (SCN) may vary with the circadian cycle. In order to start to examine this hypothesis, optical techniques were utilized to estimate resting Ca2+ levels in SCN cells in a rat brain slice preparation. [Ca2+]i measured from the soma was(More)
The goal of this study is to investigate the possible circadian regulation of hippocampal excitability and long-term potentiation (LTP) measured by stimulating the Schaffer collaterals (SC) and recording the field excitatory postsynaptic potential (fEPSP) from the CA1 dendritic layer or the population spike (PS) from the soma in brain slices of C3H and C57(More)
Migration of oligodendrocyte progenitor cells (OPCs) from proliferative zones to their final location in the brain is an essential step in nervous system development. Golli proteins, products of the myelin basic protein gene, can modulate voltage-gated Ca(2+) uptake in OPCs during process extension and retraction. Given the importance of process(More)
Many patients with Huntington's disease (HD) exhibit disturbances in their daily cycle of sleep and wake as part of their symptoms. These patients have difficulty sleeping at night and staying awake during the day, which has a profound impact on the quality of life of the patients and their care-givers. In the present study, we examined diurnal and(More)
Genes responsible for generating circadian oscillations are expressed in a variety of brain regions not typically associated with circadian timing. The functions of this clock gene expression are largely unknown, and in the present study we sought to explore the role of the Per2 (Period 2) gene in hippocampal physiology and learned behaviour. We found that(More)