Abstract
Abstract: :
Purpose: Acetylcholine (ACh) affects the response properties of many ganglion cells (GC); nAChRs have been found on dendrites of some GABAergic and glycinergic cells indicating that the release of inhibitory transmitters may be partially under cholinergic control (Dmitrieva, et al., 2001; in press). We investigated whether or not non-cholinergic cholinoceptive inhibitory interneurons express glutamate receptors, thereby providing a substrate for dual control of inhibitory neurotransmitter release. Methods: Rabbit retinas were fixed in 4% paraformaldehyde for 30 minutes and cryoprotected in 30% sucrose buffer. 8-10 µm frozen vertical and flat sections were cut and incubated in antibodies directed against GABA or glyt-1 (a polyclonal glycine transporter-1 Ab), and GluR2/3 and mAb210 (a monoclonal Ab that recognizes α3ß2 nAChRs in rabbit retina). Sections processed for immunofluorescence were examined with confocal microscopy. Results: Vertical sections showed staining patterns similar to previous reports for GABA, glyt-1, mAb210 and GluR2/3. GluR2/3 labeling was also evident in somata in the INL and GCL. Colocalization of GluR2/3 and GABA, mAb210 or glyt-1 was evident in populations of cells in the INL. Some cells displayed GluR2/3-mAb210-glyt-1 or GluR2/3-mAb210-GABA immunoreactivity (IR). Cell counts of flat sections revealed 33% of mAb210-positive cells in the central retina were GluR2/3 IR. Confocal imaging of the IPL revealed overlapping punctate GluR2/3 and mAb210 label, suggesting that some AMPA and α3ß2 nAChRs may be colocalized. Conclusions: Many of the inhibitory interneurons in rabbit retina express both GluR2/3 and mAb210 immunoreactivity. Previous reports have shown that some mAb210-positive AC are GABAergic; many are glycinergic. Taken together, these data indicate that a substrate exists for the control of inhibitory neurotransmitter release from some retinal neurons by both glutamate and ACh.
Keywords: amacrine cells • excitatory neurotransmitters • inhibitory neurotransmitters