Molecular mechanisms and regulation of opioid receptor signaling

Cloning of multiple opioid receptors has presented opportunities to investi gate the mechanisms of multiple opioid receptor signaling and the regulatio n of these signals. The subsequent identification of receptor gene structur es has also provided opportunities to study the regulation of receptor gene expression and to manipulate the concentration of the gene products in viv o. Thus, in the current review, we examine recent advances in the delineati on basis for the multiple opioid receptor signaling, and their regulation a t multiple levels. We discuss the use of receptor knockout animals to inves tigate the function and the pharmacology of these multiple opioid receptors , The reasons and basis for the multiple opioid receptor are addressed.