Circadian Regulation of Hippocampal Long-Term Potentiation

Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, California 90024-1759, USA.
Journal of Biological Rhythms (Impact Factor: 2.77). 07/2005; 20(3):225-36. DOI: 10.1177/0748730405276352
Source: PubMed


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 mice. These 2 strains of mice were of interest because the C3H mice secrete melatonin rhythmically while the C57 mice do not. The authors found that the magnitude of the enhancement of the PS was significantly greater in LTP recorded from night slices compared to day slices of both C3H and C57 mice. They also found significant diurnal variation in the decay of LTP measured with fEPSPs, with the decay slower during the night in both strains of mice. There was evidence for a diurnal rhythm in the input/output function of pyramidal neurons measured at the soma in C57 but not C3H mice. Furthermore, LTP in the PS, measured in slices prepared during the day but recorded during the night, had a profile remarkably similar to the night group. Finally, PS recordings were carried out in slices from C3H mice maintained in constant darkness prior to experimentation. Again, the authors found that the magnitude of the enhancement of the PS was significantly greater in LTP recorded from subjective night slices compared to subjective day slices. These results provide the 1st evidence that an endogenous circadian oscillator modulates synaptic plasticity in the hippocampus.

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Available from: Christopher S Colwell, Dec 12, 2013
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    • "The presence of melatonin receptors in the SCN describes its direct action where, together with serotonin (via 5-HT 2C receptors), it establishes the biorhythms of the master clock that in turn modifies brain stem monoamine release. Its presence in other limbic brain regions suggests a central role for melatonin in circadian regulation of regional brain function, such as hippocampal plasticity (Chaudhury et al., 2005) and the circadian pattern of clock gene expression in hippocampal neurons (Wakamatsu et al., 2001; Jilg et al., 2010). Both MT 1 and MT 2 receptors are 7-trans- membrane, G protein-coupled receptors acting via Gi proteins (Tardito et al., 2012). "
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    • "However, it is unclear how its rhythmic expression leads to such behavioral changes. Vesicle transporter activity throughout the brain (Darna et al., 2009) and changes in hippocampal synaptic plasticity (Chaudhury et al., 2005) exhibit diurnal variations; similarly, modulation of neurotransmitter function by the circadian clock provide potential ways through which circadian molecular mechanisms may be translated into diurnal electrophysiological and behavioral changes. "
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    • "compared with control. Scale bar 0 100 μm al. 1999; Bova et al. 1998), 5-HT 2C receptor mRNA expression , glucocorticoid receptor and mineralocorticoid receptor mRNA expression (Holmes et al. 1995, 1997), the responsiveness of pyramidal cells to norepinephrine, acetylcholine, and 5-HT (Brunel and de Montigny 1987), the activity of mitogen-activated protein kinase and cyclic adenosine monophosphate (Eckel-Mahan et al. 2008), and hippocampal excitability and long-term potential (Chaudhury et al. 2005). "
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