Mi1 [FBbt_00003776]

Mi1

ID: FBbt_00003776

Unicolumnar medullary intrinsic neuron with bushy, fine arborizations in medulla layers M1, M5 and M9-10 (Fischbach and Dittrich, 1989; Kind et al., 2021). The projection of this neuron branches at the inner-face of the medulla to form two to three varicose recurrent terminal specializations that extend back up to the inner border of layer M8 (Fischbach and Dittrich, 1989; Morante and Desplan, 2008). In central (non-dorsal margin) columns it receives input from an R8 photoreceptor cell, but connections are substantially weaker in dorsal margin columns (Kind et al., 2021). Pre-synaptic terminals are present mainly in medulla layers M9-M10, but also in all other layers where neurites extend laterally (Pankova and Borst, 2017). It receives input from lamina monopolar neurons L1 and L5 and centrifugal neuron C2 (Takemura et al., 2013). It outputs to T4 neurons and transmedullary neuron Tm3a (Takemura et al., 2013). It is a cholinergic neuron (Hasegawa et al., 2011; Pankova and Borst, 2017). There is usually one of these cells per optic column (Nern et al., 2025).

Pre-synaptic terminals were assessed by labelling with a UAS-Synaptotagmin reporter (P{UAS-HA-syt} - FBtp0015803). The neurotransmitter was assessed by labelling cells with an anti-ChAT antibody (Hasegawa et al., 2011). The morphology of the terminals was judged from figures in Fischbach and Dittrich (1989) as assessed by FlyBrain Neuron DB. Connectivity and morphology in the medulla were assessed by electron microscopy reconstruction from 7 columns (Takemura et al., 2013).