OPIOID-RECEPTOR MESSENGER-RNA EXPRESSION IN THE RAT CNS - ANATOMICAL AND FUNCTIONAL IMPLICATIONS

The cloning of the opioid receptors has profoundly affected our unders tanding of opioid-receptor expression, regulation and function. This r eview focuses on the impact that cloning has had on our understanding of opioid-receptor anatomy, and provides broad anatomical maps of the three opioid-receptor mRNAs in relation to their binding sites. In add ition, three model anatomical systems, the nigrostriatal and mesolimbi c dopamine systems, the hypothalamic neuroendocrine axes, and the asce nding and descending pain pathways, have been highlighted to discuss i ssues of receptor transport, trafficking and pre- versus postsynaptic localization.