Meeting Abstract

23.3  Jan. 5  In vivo activity of zebrafish inhibitory spinal interneurons across behaviours LIAO, James C.; Cornell University jl10@cornell.edu

Inhibitory commissural spinal interneurons play a key role in shaping the rhythmicity underlying undulatory locomotion. Here we present data on the morphology, activity, and possible interconnectivity of these cell types in 2-5 day post-fertilization zebrafish larvae obtained by targeted patch clamping in a stable transgenic line of zebrafish expressing green fluorescent protein in glycinergic cells. Commissural bifurcating longitudinal interneurons (CoBLs) are active during swimming frequencies of 30-60 hz and have motor neurons and other CoBLs as likely postsynaptic targets (as indicated by confocal imaging). Some CoBLs have a relatively long descending axon (> 4 myotomes) compared to the ascending axon while others have short ascending and descending axons (< 2 myotomes). Long-axon CoBLs are active at swimming frequencies of 30-60 Hz, as well as during struggling, when the body wave passes caudal to rostral. Short-axon CoBLs are active at 30-40 Hz and not during struggling. Commissural longitudinal ascending interneurons (CoLAs) are not active during swimming at any frequency, but rather are only recruited during struggling. Their likely post-synaptic targets include motor neurons. Commissural local interneurons (CoLOs) have a high threshold for firing and possess a short, robust descending axon that is excited by the descending reticulospinal Mauthner axon. These cells are not active during swimming or struggling, but are active during the escape response, as has been found in goldfish. Commissural secondary ascending interneurons (CoSAs) are active during swimming at 30-40 Hz as well as during struggling. Our data suggest that some cell types are dedicated to particular behaviors, whereas others are shared among behaviors. The challenge now is to understand better their ability to serve either more generalized or specific behavioral roles.