Biology subjects

Samara, E.

Publications and source records attributed to Samara, E..

2 recordsLinked to original sources

bioRxiv2025

Polyadic synapses introduce unique wiring architectures in T5 cells of Drosophila

Connectomes provide neuronal wiring diagrams and allow for investigating the detailed synaptic morphology of each connection. In the visual system of Drosophila, T5 cells are the primary motion-sensing neurons in the OFF-pathway. On their dendrites, they receive input from the excitatory Tm1, Tm2, Tm4, Tm9 and the inhibitory CT1 neurons in a spatial arrangement which depends on their preferred direction. This connectivity, however, has not yet been investigated with respect to specific types of polyadic synapses which are known to be abundant in the fly nervous system. In this study, we use the FlyWire database and identify that Tm and CT1 cells wire on T5a dendrites via eight polyadic synapse types. We then explore the distribution of the different synapse types on T5a dendrites and find differences in their spatial patterns. Finally, we show that the polyadic morphology is setting a directional wiring architecture at the T5 network level. Our work showcases the complexity that polyadic synapses introduce in T5 connectivity.

neuroscience↗

bioRxiv2024

Columnar cholinergic neurotransmission onto T5 cells of Drosophila

Several nicotinic and muscarinic acetylcholine receptors (AChRs) are expressed in the brain of Drosophila melanogaster. However, the contribution of different AChRs to visual information processing remains poorly understood. T5 cells are the primary motion-sensing neurons in the OFF pathway and receive input from four different columnar cholinergic neurons, Tm1, Tm2, Tm4 and Tm9. We reasoned that different AChRs in T5 postsynaptic sites might contribute to direction selectivity, a central feature of motion detection. We show that the nicotinic nAChR1, nAChR4, nAChR5 and nAChR7 subunits localize on T5 dendrites. By targeting synaptic markers specifically to each cholinergic input neuron, we find a prevalence of the nAChR5 in Tm1-, Tm2- and Tm4-to-T5 synapses and of nAChR7 in Tm9-to-T5 synapses. Knock-down of nAChR4, nAChR5, nAChR7, or mAChR-B individually in T5 cells alters the optomotor response and reduces T5 directional selectivity. Our findings indicate a differential contribution of postsynaptic receptors to input visual processing and, thus, to the computation of motion direction in T5 cells.

neuroscience↗