The correction of alpha7 nicotinic acetylcholine receptor concentration-response relationships in Xenopus oocytes

The rapid desensitization of alpha 7 nicotinic acetylcholine receptors (nAC hR) has presented a serious problem for the characterization of this recept or subtype, potentially confounding the interpretation of concentration-res ponse relationships. However, the consistency of cell geometry and solution flow in oocyte recordings permits estimations of instantaneous concentrati ons to be made in this system. Results interpreted with predicted instantan eous concentrations suggest that estimates of EC50 derived from conventiona l analysis may overestimate the actual EC50 values by a factor of 10 and un derestimate Hill slopes by a factor of 2-3. If the limiting desensitization process of alpha 7 receptors is driven by the agonist concentration itself rather than by time-dependent processes, then similar dependencies may exi st between the response and instantaneous agonist concentration in other sy stems. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.