The identification of novel structural compound classes exhibiting high affinity for neuronal nicotinic acetylcholine receptors and analgesic efficacy in preclinical models of pain.

Neuronal nicotinic acetylcholine receptors represent a new and potentially useful target for the development of novel non-opioid, non-NSAID (nonsteroidal antiinflammatory drug) analgesic agents. A variety of nicotinic acetylcholine receptor agonists such as nicotine, epibatidine and the azetidinyl ether, (R)-5-(2-azetidinylmethoxy-2-chloropyridine (ABT-594) possesses significant efficacy in preclinical models of pain. A preponderance of evidence suggests that nicotinic acetylcholine receptor agonists produce their analgesic effects predominantly via activation of descending inhibitory pain pathways originating in the key brainstem regions of the nucleus raphe magnus, dorsal raphe, and locus coeruleus, and that alpha4-containing nicotinic acetylcholine receptor subunits mediate these effects. Although these studies may provide a pharmacological target for the development of nicotinic acetylcholine receptor analgesics, the rational design of selective ligands based on the protein structure of the binding site is hampered by insufficient structural information. Using an approach based upon homology to known high-affinity ligands for the alpha4beta2 binding site, a four-point model is proposed which defines distance and directionality parameters common to this set of nicotinic acetylcholine receptor ligands.