Tm4 [FBbt_00003792]

Tm4

ID: FBbt_00003792

Transmedullary narrow field neuron that terminates in lobula layers 1, 2 and 4 with bleb-type arborizations, and with fine arborizations in layer 3. It displays fine arborizations in medulla layers M2, M3, M4 and M9, and has bleb-type arborizations in layers M2, M4, and M9 (Morante and Desplan, 2008; Fischbach and Dittrich, 1989). In the medulla, receives input from lamina monopolar neuron L2 and centrifugal neuron C3 (Takemura et al., 2013). In lobula layer 1, it outputs to T5 neurons (Shinomiya et al., 2014). It seems to be capable of both cholinergic and GABAergic neurotransmission. There is usually one of these cells per optic column (Nern et al., 2025).

The acetylcholine neurotransmitter was assessed by co-labelling cells with a Cha-GAL4.7.4 driver (FBtp0014830) and an anti-ChAT antibody (Varija Raghu et al., 2011), and by scRNAseq detection of choline acetyltransferase (FBgn0000303) and vesicular acetylcholine transporter (FBgn0270928) expression (Davis et al., 2020). The GABA neurotransmitter was assessed by the intersection of the expression of the VGAT-GAL4 driver (FBtp0069181) and an antibody against GABA (Raghu et al., 2013). Pre- versus postsynaptic innervation judged by scoring of terminal morphology from figures in Fischbach and Dittrich (1989) as assessed by FlyBrain Neuron DB. Connectivity in the medulla was extrapolated from serial EM from 7 columns (Takemura et al., 2013). Connectivity in the lobula was assessed by serial section electron microscopy of a single column (Shinomiya et al., 2014).