From inverse agonism to 'Paradoxical Pharmacology'

The constitutive or spontaneous activity of G protein-coupled receptors (GPCRs) and compounds acting as inverse agonists is a recent but well-established phenomenon. Dozens of receptor subtypes for numerous neurotransmitters and hormones have been shown to posses this property. However, do to the apparently low percentage of receptors in the spontaneously active state, the physiologic relevance of these findings remains questionable. The possibility that the reciprocal nature of the effects of agonists and inverse agonists may extend to cellular signaling is discussed, and that this may account for the beneficial effects of certain beta-adrenoceptor inverse agonists in the treatment of heart failure. (C) 2003 Elsevier Science B.V All rights reserved.