L1 [FBbt_00003719]

L1

ID: FBbt_00003719

Lamina monopolar neuron that has short collaterals projecting radially from the main projection in the lamina and arborization in medulla layers M1 and M5 (Fischbach and Dittrich, 1989; Kind et al., 2021). In the lamina, these short collaterals are strongly postsynaptic to the terminals of photoreceptors R1-6 (Rivera-Alba et al., 2011). In the medulla, it makes strong reciprocal synaptic connections with lamina monopolar cell L5 and centrifugal neuron C2, as well as substantial output synapses to C3, Mi1 and Tm3 cells (Takemura et al., 2013). It is also electrically synapsed to lamina monopolar neuron L2 (Joesch et al., 2010). It is a glutamatergic neuron (Gao et al., 2008; Takemura et al., 2011). There is usually one of these cells per optic column (Nern et al., 2025).

The neurotransmitter was assessed by labelling cells with a vGlut[OK371]-dVP16AD-GAL4 driver (FBti0129742) (Gao et al., 2008) or by single cell RT-PCR with specific primers (Takemura et al., 2011). Cell connectivity in the lamina was determined by analysis of semi-automated EM reconstruction of 749 serial sections of 21 complete lamina cartridges. The number of synaptic connections for L1 (presynaptic/postsynaptic) in a single lamina cartridge with each cell type was the following: R1 (-/40), R2 (-/43), R3 (-/37), R4 (-/38), R5 (-/38), R6 (-/45), L2 (-/3), Lai (-/1), C3 (-/3) and Lawf (-/1) (Rivera-Alba et al., 2011). Connectivity in the medulla was extrapolated from serial EM of 7 columns from a single sample (Takemura et al., 2013). Electrical connectivity was shown by dye labelling (Joesch et al., 2010).