Motor development and its plasticity in zebrafish

Abstract

Zebrafish is a good vertebrate model to study motor development. Zebrafish show touch response and auditory startle response at the onset of 1 day and 3 day of development, respectively. At 5 day, zebrafish also show the plasticity of auditory startle response, in which they cease to show sound-induced escape response after they repetitively hear white noise sound at subthreshold level (insufficient in loudness to evoke an escape response). When they hear the white noise, a protein kinase CaMKII is activated in the hindbrain Mauthner cells, which is the command neuron for the auditory startle response. Activated CaMKII induces phosphorylation of the scaffolding protein gephyrin at inhibitory synapse that in turn enhances synaptic accumulation of inhibitory GlyR proteins. Reinforcement of the inhibitory inputs into the Mauthner cells suppresses the Mauthner cell activation, thereby reducing the probability of auditory startle response. In general, fish is intrinsically sensitive to a splash sound, and the white noise that can reduce the escape response is identical to the sound of rain. We therefore assume that fish is endowed with a capacity to change splash (e.g. bird attack diving into water)-induced escape behavior for the adaptation to weather change.