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- Title
Strychnine, but not PMBA, inhibits neuronal nicotinic acetylcholine receptors expressed by rabbit retinal ganglion cells.
- Authors
J.M. RENNA; C.E. STRANG; F.R. AMTHOR; K.T. KEYSER
- Abstract
Strychnine is considered a selective competitive antagonist of glycine gated Cl−channels (Saitoh et al., 1994) and studies have used strychnine at low micromolar concentrations to study the role of glycine in rabbit retina (Linn, 1998; Protti et al., 2005). However, other studies have shown that strychnine, in the concentrations commonly used, is also a potent competitive antagonist of 7 nicotinic acetylcholine receptors (nAChRs; Matsubayashi et al., 1998). We tested the effects of low micromolar concentrations of strychnine and 3-2′-phosphonomethyl1,1′-biphenyl-3-yl alanine (PMBA), a specific glycine receptor blocker (Saitoh et al., 1994; Hosie et al., 1999) on the activation of both 7 nAChRs on retinal ganglion cells and on ganglion cell responses to a light flash. Extracellular recordings were obtained from ganglion cells in an isolated retinachoroid preparation and 500 M choline was used as an 7 agonist (Alkondon et al., 1997). We recorded from brisk sustained and brisk transient OFF cells, many of which have been previously shown to have 7 receptors (Strang et al., 2005). Further, we tested the effect of strychnine, PMBA and -bungarotoxin on the binding of tetramethylrhodamine -bungarotoxin in the inner plexiform layer. Our data indicates that strychnine, at doses as low as 1.0 M, can inhibit the 7 nAChR-mediated response to choline, but PMBA at concentrations as high as 0.4 M does not. Binding studies show strychnine and -bungarotoxin inhibit binding of labeled -bungarotoxin in the IPL. Thus, the effects of strychnine application may be to inhibit glycine receptors expressed by ganglion cell or to inhibit amacrine cell 7 nAChRs, both of which would result in an increase in the ganglion cell responses. Further research will be required to disentangle the effects of strychnine previously believed to be caused by a single mechanism of glycine receptor inhibition.
- Subjects
STRYCHNINE; GLYCINE; RETINA; ACETYLCHOLINE; RETINAL ganglion cells
- Publication
Visual Neuroscience, 2007, Vol 24, Issue 4, p503
- ISSN
0952-5238
- Publication type
Article
- DOI
10.1017/S0952523807070241