L2 [FBbt_00003720]

L2

ID: FBbt_00003720

A lamina monopolar neuron with short collaterals that project radially from the main projection in the lamina and that arborizes in medulla layer M2. In the lamina it receives strong input from photoreceptors R1-R6 (Rivera-Alba et al., 2011). It has both pre- and postsynaptic connections in medulla layer M2, with strong synaptic input coming from centrifugal neurons C2 and C3 (Takemura et al., 2013). It has a large number of presynaptic connections to lamina monopolar neuron L5, columnar neuron T1, and transmedullary neurons Tm1, Tm2 and Tm4 (Takemura et al., 2013). It is a cholinergic neuron (Takemura et al., 2011) and is electrically synapsed to lamina monopolar neuron L1 (Joesch et al., 2010). There is usually one of these cells per optic column (Nern et al., 2025).

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 L2 (presynaptic/postsynaptic) in a single lamina cartridge with each cell type was the following: R1 (1/46), R2 (1/45), R3 (-/39), R4 (-/41), R5 (-/39), R6 (-/47), L1 (3/-), L4 (10/7), L5 (1/-), Lai (-/1), C2 (-/3), C3 (-/5) and Lwf (-/7) (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). Note that for many of the output synapses in M2, Tm1 and Tm2 share the same sites (Takemura et al., 2008; Takemura et al., 2011). Electrical connectivity was shown by dye labelling (Joesch et al., 2010). The neurotransmitter was assessed by single cell RT-PCR measurement of choline acetyltransferase (FBgn0000303) expression (Takemura et al., 2011).