Posts Tagged ‘anaesthesia’

Mechanisms of anaesthesia

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General anaesthetic photolabels are used to find the molecular binding sites of anaesthetics, such as GABA receptors, protein kinase and tubulin. Involvement of anaesthetics with voltage-dependent channels for negative ions and the mitochondria has been demonstrated by photolabelling. At clinical concentrations anaesthetics can effect the functioning of proteins. Photolabels can attach to residues or individual molecules lining protein pockets, and thus indicate the presence of a dynamic ligand in a pocket.

Anaesthetics and brain energy

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Brain regions where there is an increase in functional energetic demand have a corresponding increase in glucose metabolism, their metabolic rate for oxygen and their cerebral blood flow. Cerebral energy is seen as depending on the oxidation of glucose. Cerebral blood flow similarly tracks energy consumption.

Brain’s Resting State

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The brain’s resting state activity accounts for about 80% of its energy consumption. Anaesthesia, in which consciousness is removed, involves a 40-50% reduction in energy consumption, implying that part of the resting state’s high level of energy consumption is used to sustain consciousness. The resting state also overlaps with the reward system which is based on midline structures, as distinct from lateral regions that are more involved in planning and reasoning.

Energy and consciousness

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The authors argue that the conscious state is supported by a high and fairly uniform baseline energy consumption and related levels of neural activity. This viewed is based on PET scanning measures of glucose and oxygen consumption, taken with subjects under anaesthesia, that showed that energy levels while under anaesthesia are 40-50% below awake resting levels across different brain regions.

Recovery of consciousness

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Recovery of consciousness after anaesthesia is argued to involve particular brain hubs that are active for periods of minutes before processing moves to another brain hub in an orderly sequence. The findings here can be related to recent consciousness studies, which points towards conscious processing being the function of intense activity in restricted regions or hubs of the brain.

Implications of anaesthesia

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Into the void (on anaesthetics) Linda Geddes New Scientist, 26 November 2011 This article highlights an important change in the understanding of anaesthetics during the last part of the twentieth century. Previously it had been thought that anaesthetics worked by disrupting the lipid membranes of neurons. Later experiments showed that anaesthetics can bind to receptor proteins. The widely used anaesthetic, Propofol, binds to receptors for the inhibitory neurotransmitter, GABA. Studies by Read more […]