Anatomical and genotype-specific mechanosensory responses in Drosophila melanogaster larvae.
Afferent neurons commonly exhibit a somatotopic arrangement in the central nervous system that organizes spatially discrete sensory input. We are interested in how that spatial input gets integrated into motor commands. With resources for screening genes and neural circuits, and given that the cells and ion channels that transduce tactile stimuli in Drosophila larvae are remarkably well-characterized, larval mechanosensation is an ideal system for investigating how specific behaviors emerge from localized sensory input. We observed that crawling larvae are more reactive to a 20mN tactile stimulus on the head than on the tail or abdomen. Behavioral responses that were evoked by the stimuli also depended on where the stimulus was delivered. Differences in relative sensitivity were observed in different genotypes, e.g., a null white mutant and hypomorphic smn mutant are significantly more reactive to tail touches than Canton-S larvae. Responses were inhibited by silencing chemical transmission in a combination of multidendritic and chordotonal neurons, but not by inhibiting any specific subset of neurons. Extracellular recordings from segmental nerves revealed that sensory-evoked responses exhibit spike-timing dependence at the neural circuit level. Tactile stimuli reduced endogenous firing frequency and increased bursting periods when applied during periods of motor activity. The same stimulus initiated bursts of activity when applied during inactive periods. Together, these data depict the spatial and temporal complexity of mechanosensation as it applies to action selection, and provide a foundation for addressing how neural circuits in the CNS adjust their activity to afferent input.
Department of Biology, University of Kentucky, Lexington, KY 40506, USA. Electronic address: joshtitlow@uky.edu.
Josh S
JS
Titlow
Department of Biology, University of Kentucky, Lexington, KY 40506, USA; Transylvania University, Lexington, KY 40508, USA.
Jordan
J
Rice
Department of Biology, University of Kentucky, Lexington, KY 40506, USA; Department of Biology, College of Science, University of Salahaddin, Erbil, Iraq.
Zana R
ZR
Majeed
Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
Emily
E
Holsopple
Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
Stephanie
S
Biecker
Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
Robin L
RL
Cooper
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics; D004331:Drosophila melanogaster / Q000502:physiology*; D004594:Electrophysiology; D005136:Eye Proteins / Q000235:genetics; D055786:Gene Knockout Techniques; D005838:Genotype; D007814:Larva; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D016601:RNA-Binding Proteins / Q000235:genetics; D014110:Touch / Q000502:physiology
D018528:ATP-Binding Cassette Transporters; D029721:Drosophila Proteins; D005136:Eye Proteins; D016601:RNA-Binding Proteins; C542563:Smn protein, Drosophila; C059254:w protein, Drosophila
Behavior; Crawling; Drosophila melanogaster larva; Electrophysiology; Mechanosensory