Interaction of HEPES analogues with high and low affinity alpha4beta2 nicotinic acetylcholine receptors

Positive allosteric modulators (PAMS) can enhance responses of neuronal alpha7 and alpha4beta2 nicotinic acetylcholine receptor (nAChR) subtypes to orthosteric ligands. PAMS represent new leads for the development of therapeutic agents for disorders involving alterations in nicotinic neurotransmission. We previously identified 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid (HEPES) as a stoichiometric selective PAM for the high affinity alpha4beta2 nAChR. In this study, we investigated the selective nature of HEPES interactions using a series of HEPES analogues. Compounds were evaluated in a phosphate buffered recording buffer using two electrode voltage clamp techniques and alpha4beta2 nAChRs expressed in Xenopus laevis oocytes. The majority of compounds tested were unable to potentiate acetylcholine (ACh) induced responses on either high or low affinity alpha4beta2 nAChRs. However, several compounds produced a selective enhancement of ACh induced responses on the high affinity receptor. The specific structural requirements for potentiation of the high affinity receptors suggest that these molecules may serve as novel leads to the development of new agents selective for high affinity receptors. National Center for Research Resources (5P20RR016466 and 1R01NS066059).