Molecular mechanisms underlying recovery from general anaesthesia (2016–2018)
This is a basic neuroscience research proposal aimed at understanding fundamental mechanisms of general anaesthesia. Most of us will require general anaesthesia at some time in our lives. While this extremely common procedure has become quite safe, there are some aspects of general anaesthesia that remain problematic. In particular, whereas anaesthesia induction is understood to involve the activation of sleep pathways in the brain (usually achieved via GABA agonists such as propofol), it is unclear how volatile anaesthetics (such as isoflurane) maintain sedation, and why recovery from the procedure can be quite variable among patients, especially patients with cognitive disorders or dementia. We have discovered that general anaesthetics (both isoflurane and propofol) impair neurotransmitter release from neurons, and we propose that this relatively subtle effect across all synapses leads to a loss of functional connectivity in the brain, which is the endpoint that makes surgery possible ¿¿¿ but which by extension also complicates recovery among some patients. To better understand this secondary mechanism of general anaesthesia (after sleep induction), we turn to a simpler model that allows for efficient genetic analysis as well as electrophysiology, the fly Drosophila melanogaster. We will use genetic manipulations in Drosophila to dissect synaptic release processes from sleep processes, to better understand the relative contribution of each to anaesthesia induction, maintenance, and recovery (aim1). We will then use mammalian cell lines to elucidate how general anaesthetics impair synaptic release (aim2). Finally, we will use a whole-brain recording preparation for flies to understand how synaptic manipulations modulate functional connectivity in the brain under general anaesthesia (aim3). These experiments will reveal an alternate mechanism that is likely to be more relevant for anaesthesia maintenance and recovery than the current sleep-centred theories.