Inhibition and motor control in the developing zebrafish spinal cord

•Inhibitory spinal interneurons are important regulators of locomotor activity.•The function and developmental origin of many remains uncharacterized.•The zebrafish allows genetic targeting and morphological analysis of spinal neurons.•Probing the function of population of spinal neurons is possible with new optical tools.

Vertebrate locomotion relies on oscillatory activity along the spinal cord. Inhibition is involved in controlling the alternation of activity between each side and contributes in modulating propagation and termination of locomotor activity. Spinal inhibitory neurons are thought to regulate these mechanisms but the exact contribution of specific cell types remains difficult to tackle during active locomotion. In the past two decades, use of the transparent zebrafish larva has enabled morphological, functional, and genetic characterization of specific inhibitory spinal neurons. A wide range of new optical tools has been developed to monitor and to manipulate the activity of genetically targeted spinal populations. Combining these techniques with conventional electrophysiology will provide a better understanding of the contribution of inhibitory spinal interneurons in regulating essential features of locomotor patterns.