I am very much impressed by a study that appeared in a recent issue of Journal of Neuroscience. The researchers used electrophysiological techniques to measure neuronal output indicative of sleep in vitro, bioluminescent imaging to measure daily rhythms of a luciferase-expressing circadian gene, standard molecular benchwork to characterize changes in levels of gene expression and phosphorylation, and mass spectrometry to identify changes in metabolic pathways. WOW.
The focus was on a wake-promoting pharmacologic that was applied to neurons in a dish in order to compare with forced wakefulness in a live animal . Upon application of the pharmacologic in vitro, the firing rate of neurons ceased to be single-burst, which is a cell culture marker of sleep, and became highly chaotic for up 24 hrs after it is applied.
Second, Changes in gene expression prior to, during, and after the application of the wake-promoting pharmacologic in vitro were nearly to identical under conditions of forced wakefulness in vivo.
Further, changes in the expression of metabolites, namely those of lipid pathways, were nearly identical in the stimulated neurons compared with sleep-deprived animals.
There is certainly a lot more to this study than that which I summarize here, so I encourage everyone who has an interest in basic sleep research to read the paper. It was unclear to me exactly what the pharmacologic was. The researchers did not spend much time on pharmacology, and I’m uncertain whether it was wake-promoting through its actions on histaminergic, GABAergic, serotonergic, cholinergic, or any other neuromodulatory or small molecule pathway that regulates wakefulness. At any rate, the variety in experimentation at behavioral, physiological, neuronal, molecular, and genomic levels is impressive. Perhaps it is one of the author’s entire dissertation work?
Hinard V, Mikhail C, Pradervand S, Curie T, Houtkooper RH, Auwerx J, Franken P, & Tafti M (2012). Key electrophysiological, molecular, and metabolic signatures of sleep and wakefulness revealed in primary cortical cultures. The Journal of neuroscience : the official journal of the Society for Neuroscience, 32 (36), 12506-17 PMID: 22956841