Molecular mechanisms of sleep and wakefulness.

Mackiewicz M, Naidoo N, Zimmerman JE, Pack AI

Molecular mechanisms of sleep and wakefulness.

Ann N Y Acad Sci. 2008;1129:335-49

Authors: Mackiewicz M, Naidoo N, Zimmerman JE, Pack AI

Major questions on the biology of sleep include the following: what are the molecular functions of sleep; why can wakefulness only be sustained for defined periods before there is behavioral impairment; what genes contribute to the individual differences in sleep and the response to sleep deprivation? Behavioral criteria to define sleep have facilitated identification of sleep states in a number of different model systems: Drosophila, zebrafish, and Caenorhabditis elegans. Each system has unique strengths. Studies in these model systems are identifying conserved signaling mechanisms regulating sleep that are present in mammals. For example, the PKA-CREB signaling mechanism promotes wakefulness in Drosophila, mice, and C. elegans. Microarray studies indicate that genes whose expression is upregulated during sleep are involved in macromolecule biosynthesis (proteins, lipids [including cholesterol], heme). Thus, a key function of sleep is likely to be macromolecule synthesis. Moreover, in all species studied to date, there is upregulation of the molecular chaperone BiP with extended wakefulness. Sleep deprivation leads to cellular ER stress in brain and the unfolded protein response. Identification of genes regulating sleep has the potential for translational studies to elucidate the genetics of sleep and response to sleep deprivation in humans.

PMID: 18591493 [PubMed - indexed for MEDLINE]

NbActiv4 medium improvement to Neurobasal/B27 increases neuron synapse densities and network spike rates on multielectrode arrays.

Brewer GJ, Boehler MD, Jones TT, Wheeler BC

NbActiv4 medium improvement to Neurobasal/B27 increases neuron synapse densities and network spike rates on multielectrode arrays.

J Neurosci Methods. 2008 May 30;170(2):181-7

Authors: Brewer GJ, Boehler MD, Jones TT, Wheeler BC

The most interesting property of neurons is their long-distance propagation of signals as spiking action potentials. Since 1993, Neurobasal/B27 has been used as a serum-free medium optimized for hippocampal neuron survival. Neurons on microelectrode arrays (MEA) were used as an assay system to increase spontaneous spike rates in media of different compositions. We find spike rates of 0.5 s(-1) (Hz) for rat embryonic hippocampal neurons cultured in Neurobasal/B27, lower than cultures in serum-based media and offering an opportunity for improvement. NbActiv4 was formulated by addition of creatine, cholesterol and estrogen to Neurobasal/B27 that synergistically produced an eightfold increase in spontaneous spike activity. The increased activity with NbActiv4 correlated with a twofold increase in immunoreactive synaptophysin bright puncta and GluR1 total puncta. Characteristic of synaptic scaling, immunoreactive GABAAbeta puncta also increased 1.5-fold and NMDA-R1 puncta increased 1.8-fold. Neuron survival in NbActiv4 equaled that in Neurobasal/B27, but with slightly higher astroglia. Resting respiratory demand was decreased and demand capacity was increased in NbActiv4, indicating less stress and higher efficiency. These results show that NbActiv4 is an improvement to Neurobasal/B27 for cultured networks with an increased density of synapses and transmitter receptors which produces higher spontaneous spike rates in neuron networks.

PMID: 18308400 [PubMed - indexed for MEDLINE]

Cholesterol & Synapse Research News

Molecular mechanisms of sleep and wakefulness.

NbActiv4 medium improvement to Neurobasal/B27 increases neuron synapse densities and network spike rates on multielectrode arrays.