Native brain and heterologously expressed rat α4β2 nicotinic receptors (in Xenopus oocytes and CV-1 cells) were immunoisolated with the anti-α4 antibody mAb 299 and their pharmacological properties were compared using [3H](±)epibatidine, the novel N-alkylnicotinium analog N-n-octylnicotinium iodide (NONI), and the ganglionic antagonist trimethaphan (TRM). The equilibrium dissociation constant (Kd) for [3H](±)epibatidine binding to the native and heterologously expressed receptors ranged from 13 to 21 pM. The Hill coefficients for [3H](±)epibatidine binding to the native and expressed receptors ranged from 0.8 to 1.1 and were consistent with a single high-affinity site. NONI inhibited 30 pM [3H](±)epibatidine binding to the native and expressed receptors with similar potency (IC50 values of 6-7 μM). However, [3H](±)epibatidine dissociated 2-3 times more slowly from the native, than from the expressed receptors and TRM inhibited 30 pM [3H](±)epibatidine binding to the native receptors (IC50 value of 330 μM) less potently than it did to the receptors expressed in oocytes (IC50 value of 16 μM) or CV-1 cells (IC50 value of 55 μM). The differences between the native and expressed [3H](±)epibatidine dissociation rate constants and IC50 values for TRM were significant for both host cell types, although the values for the CV-1-expressed receptors were closer to the native ones than were those for the oocyte-expressed receptors. Thus, the epibatidine and trimethaphan binding sites in native and expressed α4β2 receptors appear to have significantly different structural or chemical properties.
|Number of pages||9|
|Journal||Molecular Brain Research|
|State||Published - Nov 30 2001|
Bibliographical noteFunding Information:
This research was supported by funds from the California Tobacco-Related Disease Research Program, award number 6KT-0208, and from the NIH, grants DA10934 and DA00399. We thank Dr. Jerry Sepinwall of Hoffman-LaRoche for providing us with the trimethaphan camsylate used in these experiments.
- Dissociation rate constant
- N-n-Octylnicotinium iodide, NONI
- Neuronal nAChR
- α4β2 Nicotinic receptor
ASJC Scopus subject areas
- Molecular Biology
- Cellular and Molecular Neuroscience