ALPHA(2)-ADRENOCEPTORS - MORE SUBTYPES BUT FEWER FUNCTIONAL DIFFERENCES

The proliferation of receptor subtypes based on differences in amino a cid sequence does not necessarily coincide with functional differences . The number of alpha(2)-adrenoceptor subtypes, as defined by ligand-b inding and molecular studies, has been increasing in the past few year s, which suggests the possibility of distinct physiological and pathol ogical pathways that could be targeted by new selective drugs. However , the evidence from functional studies has been less convincing. This could be due to the lack of sufficiently selective ligands or to the s imilarity between the activated state of receptor subtypes. Species di fferences and the local receptor environment are also important determ inants of the pharmacological profile of a particular subtype. The pha rmacology of the putative subtypes of alpha(2)-adrenoceptors and their function ave discussed in this review by Alison MacKinnon, Mike Spedd ing and Christine Brown.