Abstract
Abstract: :
Purpose:In the retina, acetylcholine (ACh) is released from the populations of ON and OFF starburst amacrine cells (Masland & Livingston, 1976; Famiglietti, 1983) and affects the response properties of a subset of retinal ganglion cells (GCs; Masland & Ames, 1976; Schmidt et al., 1987; Lipton, 1988). Many types of GCs display pharmacology consistent with cholinoception (Baldridge, 1996; Kittila & Massey, 1997; Grzywacz et al., 1998), and multiple GC classes in the rabbit retina express nAChRs (Wilkinson et al., 2001). However, to date, there has been no correlation of the expression of nAChRs and their functional properties. This study was designed to provide pharmacological evidence of expression of functional nAChRs by physiologically and morphologically identified rabbit GCs. Methods:Standard extracellular recording techniques were used to record GC light responses from retina-choroid-epithelium preparations. After physiological characterization, and bath application of pharmacological agents, sharp electrodes were used to fill the identified cells with florescent dye. The retinae were then fixed, cryoprotected and sectioned into 10-100 mm slices, and incubated with an antibody that recognizes α3ß2 nAChRs in rabbit retina (Keyser et al, 2000). Results:Nicotine application increased the spontaneous firing and enhanced the light response of a subset of brisk GCs. In addition, several classes of synaptically isolated α3ß2 expressing GCs responded to nicotine application with an increase in spontaneous firing. Conclusion:The effects of nicotine on many GCs are mediated by α3ß2 nAChRs.
Keywords: 305 acetylcholine • 541 receptors: pharmacology/physiology • 415 ganglion cells