Abstract
Abstract: :
Purpose: Three ß (ß2–ß4) and nine α subunits (α2–α10) of neuronal nAChRs have been identified. Keyser, et al, (2000) demonstrated that many amacrine cells (ACs), ganglion cells (GCs) and some displaced ACs express nAChRs that include ß2 subunits in combination with α3 and perhaps other subunits in rabbit retina. RT–PCR data have shown message for a number of other nAChR subunits in rabbit retina (Strang, et al, 2003). Our study investigated the distribution of these other subunits in rabbit retina using immunohistochemistry. Methods: Rabbit retinas were fixed, sectioned and incubated in antibodies (a gift of Dr. J. Lindstrom) directed against mAb210 (recognizes α3ß2 nAChRs in rabbit retina), and/or mAb35 (α1, 3, 5), mAb295 (ß2), mAb371 (α4) or mAb318 (α7). Sections were processed using a tyramide amplification system combined with regular 3–step immunohistochemistry, and examined with a confocal microscope. Results: As reported previously, mAb210 labeling was found in many ACs and GCs, and in processes throughout the IPL. mAb35 labeling was localized to a subpopulation of mAb210–positive ACs and their processes in the IPL. mAb295 or mAb318 labeling was found in ACs, GCs and bipolar cells (BCs) and in processes in the IPL. Many of the ACs and GCs immunoreactive for mAb295 or mAb318 were also mAb210–immunoreactive. Significant overlap of mAb210 and antibodies against ß2 or α7 was evident in punctate elements in the IPL. Subpopulations of the nAChR–positive BCs were immunopositive for the cone ON BC markers CD15 or NK–1. Conclusions: Message for a number of nAChR subunits, including α3, α4 and α7, has been identified using RT–PCR in rabbit retina (Strang, et al, 2003). The data presented here suggest that multiple nAChR subunits are differentially expressed by distinct cell types. Furthermore, the expression of nAChR subunits by identified bipolar cell populations, and the potential presence of multiple receptor subtypes on individual dendrites in the IPL in rabbit retina are novel findings, and suggest that ACh can affect the responses of many different cell types in the retina through a variety of receptors.
Keywords: acetylcholine • neurotransmitters/neurotransmitter systems • retina: proximal (bipolar, amacrine, and ganglion cells)