Neuroscience 2004 Abstract
| Presentation Number: | 275.14 |
|---|---|
| Abstract Title: | Functional expression studies of α4-containing nicotinic receptors with a Leu9´Ala gain of function mutation. |
| Authors: |
Fonck, C.*1
; Marks, M.2
; Whiteaker, P.2
; Labarca, C.1
; Nashmi, R.1
; McKinney, S.1
; Rodrigues-Pinguet, N.1
; Cohen, B. N.1
; Collins, A. C.2
; Lester, H. A.1
1Div Biol, California Inst Technol, Pasadena, CA 2CO, 1200 East California Blvd, 91125-8709, |
| Primary Theme and Topics |
Synaptic Transmission and Excitability - Ligand Gated Ion Channels -- Nicotinic acetylcholine receptors |
| Session: |
275. Nicotinic Acetylcholine Receptors: Structure and Function Poster |
| Presentation Time: | Sunday, October 24, 2004 2:00 PM-3:00 PM |
| Location: | San Diego Convention Center - Hall A-H, Board # F12 |
| Keywords: | ACETYLCHOLINE, NICOTINE, FURA-2, OOCYTE |
Previous results show that mice expressing α4-containing nicotinic receptors with a Leu9’Ala (L9´A) mutation have increased (~20-fold) sensitivity in nicotine-induced seizures compared to their wild type (WT) littermates (Fonck et al, SFN, 2003). To further characterize the L9´A mutation, nicotine and/or acetylcholine (ACh) responses were measured in: a) voltage-clamped Xenopus oocytes expressing mouse α4L9´Aβ2 and α4β2 receptors, (b) thalamic primary cell cultures obtained from heterozygous (het) and homozygous (hom) L9´A mouse embryos, and c) synaptosomes made from cortex and thalamus of het and hom L9´A mice. In oocytes, the EC50s of the nicotine and ACh concentration-response relationships showed a 30-fold decrease in L9´A compared to WT receptors. At saturating concentrations of nicotine, the maximal mutant and WT nicotine responses were similar. Fura 2-loaded cell cultures derived from L9´A embryos were ~15-25 times more sensitive to nicotine and ACh-induced increases in intracellular Ca2+ compared to WT. L9´A cells also displayed a 4-fold larger Fura 2 response than WT cells at saturating nicotine concentrations. Synaptosomes made from L9´A thalamus and cortex were 5-10 times more sensitive in the ACh-induced 86Rb+ efflux assay compared to WT. At saturating ACh concentrations, interestingly, synaptosomes obtained from hom L9´A mice had a marked reduction (70 %) in 86Rb+ efflux compared to WT. In conclusion, hypersensitive α4L9´A-containing receptors are expressed in L9´A mice but factors such as host cell type, developmental stage, and/or subcellular distribution appear to affect the level of functional L9´A expression.
Supported by TRDRP, NS11756, NS43800, NRSA
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2004 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2004. Online.
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