title: In Vivo Ca(2+) Imaging Reveals that Decreased Dendritic Excitability Drives Startle Habituation.
abstract: Exposure to repetitive startling stimuli induces habitation, a simple form of learning. Despite its simplicity, the precise cellular mechanisms by which repeated stimulation converts a robust behavioral response to behavioral indifference are unclear. Here, we use head-restrained zebrafish larvae to monitor subcellular Ca(2+) dynamics in Mauthner neurons, the startle command neurons, during startle habituation in vivo. Using the Ca(2+) reporter GCaMP6s, we find that the amplitude of Ca(2+) signals in the lateral dendrite of the Mauthner neuron determines startle probability and that depression of this dendritic activity rather than downstream inhibition mediates glycine and N-methyl-D-aspartate (NMDA)-receptor-dependent short-term habituation. Combined, our results suggest a model for habituation learning in which increased inhibitory drive from feedforward inhibitory neurons combined with decreased excitatory input from auditory afferents decreases dendritic and Mauthner neuron excitability.
authors.affiliation: Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Kurt C
authors.initials: KC
authors.lastname: Marsden
authors.affiliation: Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA. Electronic address: granatom@mail.med.upenn.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Granato
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D003712:Dendrites / Q000378:metabolism*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D007814:Larva / Q000378:metabolism; D051580:Neuronal Calcium-Sensor Proteins / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D013216:Reflex, Startle / Q000187:drug effects; D013331:Strychnine / Q000494:pharmacology; D015027:Zebrafish / Q000254:growth & development / Q000378:metabolism
chemical_list: D051580:Neuronal Calcium-Sensor Proteins; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D013331:Strychnine; D002118:Calcium