Dopamine promotes motor programs underlying substrate tunneling in larval Drosophila (dataset)

Dopamine is a conserved biogenic amine with diverse neuromodulatory roles. Here we examine dopamine’s role in modulating Drosophila melanogaster larval motor programs underlying movement over and through substrates. First, we performed dual-color calcium imaging in tyrosine hydroxylase (TH)-expressing dopaminergic neurons and motor neurons to reveal cell-type specific recruitment patterns during fictive motor programs. Activity of select TH-neurons correlated strongly with fictive headsweeps, forward and backward fictive locomotion. Next, bath applications of dopamine biased the isolated central nervous system towards forward fictive locomotion and inhibited fictive head sweeps, suggesting a behavioral transition away from navigation to direction-oriented locomotion. To probe whether these effects are recapitulated in intact animals, we optogenetically manipulated TH-neuron activity during surface crawling and tunneling. Optogenetic activation of TH-neurons with CsChrimson during crawling had no effect on headsweeps and slowed locomotor rhythms by increasing wave duration and decreasing wave frequency. Furthermore, posterior asymmetries, motor sequences characteristic of tunneling, were enhanced. On the other hand, optogenetically inhibiting TH-neurons with GtACR1 had little effect on crawling. Underground, TH-neuron activation enhanced tunneling activity by increasing wave frequency, instead of duration, to increase overall tunneling time, whereas inhibition decreased time spent tunneling. These results suggest that dopaminergic modulation of larval forward locomotion is dependent on sensorimotor context. We propose dopamine mediates a coordinated network effort to shift central pattern generators to enhance tunneling motor programs.

Repository contains all data (as .csv files) and analysis code (in jupyter notebooks) required to regenerate the figures in the paper.