The Connectivity of a Serotonin Releasing Neuron within a Fruit Fly Sensory Network

Kaylynn E. Coates, Steven A. Calle-Schuler, Victoria L. Knotts*, Brennah N. Martik, Farzaan Salman*, Lauren T. Warner*, Sophia V. Valla*, Davi D. Bock and Andrew M. Dacks, Department of Biology, West Virginia University, Morgantown, WV 26506

Field (Broad Category): Neuroscience (Biological & Biochemical Sciences) 

Student’s Major: Biology & Biochemistry 

Serotonergic modulatory neurons alter the way that neurons process information in a context-dependent manner. Serotonergic neuron populations containing tens of thousands of neurons have been shown to have heterogeneous innervation across brain regions and contain neurons with opposing influences on behavior. To understand the heterogeneity that an individual neuron can have across brain regions, we analyze the neuronal partners of a single serotonergic neuron, the CSDn, across olfactory brain regions known as glomeruli. Two contralaterally projecting, serotonin-immunoreactive deutocerebral neurons (CSDns) serve as the sole source for serotonin in the main olfactory processing regions. In this project, the synaptic partners of the CSDn were classified in nine glomeruli which vary in their odor tuning. An analysis of the regional synaptic contributions by different neuron classes will tell us if the heterogeneous innervation is associated with the specificity of those glomeruli to odorants. This project was executed by using an electron microscopy database of a female adult fruit fly brain to map the skeletons of CSDn partners and classify them into known neuron classes. Results have shown that output from the CSDns tend to be largely and consistently onto local interneurons that span across glomeruli. However, input varies widely among glomeruli with no association to odor tuning, suggesting some other connectivity schema. This shows that the input onto a single serotonergic neuron differs in a glomerulus dependent manner while the output does not, thus, demonstrating that the complexity of large populations of serotonergic neurons can be conserved at the single neuron level. 

Funding: NIH DC 016293 and a USAFOSR FA9550-17-800 1-0117 to AMD, the HHMI Janelia Research Campus Visiting Scientist Program project 801 to AMD and KEC, and a Wellcome Trust Collaborative Award (203261/Z/16/Z) and NIH 802 RF1 MH120679 01 award to DDB 

Program/mechanism supporting research/creative efforts: Biology 486 capstone