Computational modelling of functional maturation of primary motoneuron firing properties in developing zebrafish

Several ion currents of zebrafish primary motoneurons undergo changes in expression level during early development. Similarly, the firing properties of primary motoneurons and their involvement during locomotor activity change during early development as locomotor control of developing zebrafish matures. To test whether the experimentally observed changes in ion currents during development could underlie changes in firing properties and in participation during locomotor activity, we created models of primary motoneurons at developmental stages. Changes in the expression levels of a persistent outward potassium current, persistent inward potassium current, and several high-voltage activated calcium currents were modelled based on experimental observations. Simulations of our computational models replicated shifts in primary motoneuron firing properties and involvement during light-evoked swimming observed at 3 and 5 days post-fertilization. Our results suggest that developmental changes in specific ion currents of primary motoneurons could be sufficient to foster changes in firing properties of primary motoneurons that shape their activity level during maturation of motor control in developing zebrafish.