Fig. 4. Two types of AII lobules in sublamina a of the IPL. (A) An image obtained from a vertical section processed for CR immunoreactivity. Two CR-labeled AII amacrine somata can be observed in the region of the INL adjacent to the IPL, with dendrites extending through the IPL. Lobular appendages (arrows) arising from the main dendrite are distributed throughout strata 1 and 2 of the IPL, while the finer arboreal dendrites penetrate downward into strata 3 through 5, extending towards the GCL. (B, C) Triple-labeled confocal images obtained at different focal planes in the same field of a wholemount processed for TH (green), CR (red), and VGLUT1 (blue) immunoreactivity. (B) Depicts stratum 1 of the IPL, in which CR-labeled AII lobules (arrowheads) are contacted by TH-labeled DAC varicosities and the terminals of VGLUT1-labeled cone bipolar cells. (C) Depicts stratum 2 of the IPL, in which AII lobules (arrowheads) remain in contact with the terminals of cone bipolar cells, but not with DAC varicosities. (D) Distribution of AII lobules in (TH+) and out of (TH−) contact with DAC varicosities, according to depth in the IPL. The graph shows that most AII lobules in stratum 1 of the IPL are contacted by DAC varicosities, while AII lobules in deeper regions are not contacted by DAC varicosities. Scale bars=10 µm. DACs: Dopaminergic amacrine cells; TH: tyrosine hydroxylase; INL: inner nuclear layer; IPL: inner plexiform layer; CR: calretinin; GCL: granule cell layer; VGLUT1: vesicular glutamate transporter 1.
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