Synaptic integration in a circuit controlling feeding and innate escape behaviour
|Starts:||13:00 7 Jul 2015|
|Ends:||14:00 7 Jul 2015|
|What is it:||Seminar|
|Organiser:||Faculty of Life Sciences|
|Who is it for:||University staff|
This seminar is part of the Future Leaders in Neuroscience series.
Innate defensive behaviors ensure animal survival. Actions such as escaping and hiding from predators are critical for successful foraging while avoiding dangerous threats. Defensive behaviors often result in avoidance of threatening places and confinement to safe patches, yet they must allow other actions to take place even in the face of perceived threat. A key behavioural computation is therefore to match the level of risk taking to the current needs and internal motivations. We are currently exploring how hunger states influence innate defensive behaviors in the mouse, using a foraging task where animals decide between foraging for food or escaping and avoiding predator cues in the foraging area. While well-fed animals show a robust defensive sequence consisting of escape, freezing and place aversion, hungry animals show increased tolerance to threat. Using in vivo optogenetics in the Periaqueductal Gray (PAG) we have identified moleculary-defined neuron types in the dorsomedial PAG that are necessary and sufficient to trigger the innate response to visual predator cues, and that control the intensity of the defensive reaction. Furthermore, experiments in known hypothalamic feeding circuits show that ARGP neurons in the Arcuate Nucleus are a key cell population that is sufficient to inhibit defensive behaviors. Combining circuit tracing with in vitro and in vivo electrophysiology techniques to investigate synaptic integration in AGRP and PAG neurons, we have found that AGRP neurons are near-perfect synaptic integrators, whereby excitatory synaptic potentials outlast the neuronal time-constant up to 10-fold due to persistent activation of a voltage-gated sodium channel. These experiments give insight into the biological basis of innate defensive behavior suppression during hunger, and may serve as an entry point for understanding the establishment of behavioral hierarchies.
Organisation: MRC Laboratory of Molecular Biology, Cambridge
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