What is unconsciousness in a fly or a worm? A review of general anesthesia in different animal models

Isoflurane Impairs Low-Frequency Feedback but Leaves High-Frequency Feedforward Connectivity Intact in the Fly Brain

“…Flies are also rendered unresponsive by general anesthetics and in similar concentrations to humans (van Swinderen and Kottler, 2014; Zalucki and van Swinderen, 2016). Indeed, the cellular and molecular machinery that makes up the nervous system is largely conserved across species (Littleton and Ganetzky, 2000), such that the cellular and molecular targets of general anesthetics are also likely to be conserved (Sonner, 2008; van Swinderen and Kottler, 2014; Zalucki and van Swinderen, 2016).…”

“…Indeed, the cellular and molecular machinery that makes up the nervous system is largely conserved across species (Littleton and Ganetzky, 2000), such that the cellular and molecular targets of general anesthetics are also likely to be conserved (Sonner, 2008; van Swinderen and Kottler, 2014; Zalucki and van Swinderen, 2016). Whether the conserved cellular and molecular targets of general anesthetics also translate to conserved system-level general anesthetic effects, such as reduced FB, is currently unknown.…”

The effects of the general anaesthetic propofol on Drosophila larvae

“…Therefore, general anaesthesia can be described as a state of decreased responsiveness which can be assessed using a variety of behavioural endpoints. For example, in humans, implicit memory is particularly susceptible to general anaesthetics (Chortkoff et al, 1993), while movement responses to noxious stimuli and consciousness are more resistant (Zalucki and van Swinderen, 2016).…”

“…From these experiments, he was among the first to find a quantifiable relationship between the concentration of inspired anaesthetic and behavioural response (Snow, 1858). Subsequent studies on a variety of animals revealed a curious feature of general anaesthetics: most animals appear to be sedated by general anaesthetics at similar drug concentrations (Zalucki and van Swinderen, 2016). While it is difficult to make behavioural comparisons across species, the general trend seems to be that more complex behaviours (which involve multiple neural pathways or behavioural sequences)…”

“…The first clue to this possible difference is the discrepancy between adult and larval sleep behaviour. While Drosophila adults have been found to fulfil the criteria for sleep (Shaw et al, 2000;Hendricks et al, 2000), evidence for larval sleep remains contentious (Szuperak et al, 2018;Zalucki and van Swinderen, 2016). In fact, many of the key structures thought to be involved in the sleep/wake circuits (such as the dorsal fan-shaped body) do not fully develop until during the pupal stage (Riebli et al, 2013).…”