Localization of individual opioid receptor subtypes in CNS

In last decades, the research focused on opioid receptors has been intensively conducted in order to determine their role in various homeostatic functions, control of movement, neurotransmission and drug addiction. An important factor determining the pharmacologic role of opioid receptors is their distribution within the brain regions as well as at the cellular level. Over the past 40 years, a great deal of information concerning their distribution in the central nervous system has been collected, allowing us to determine their localization and mechanisms of their action. In general, results obtained from previous studies are in agreement. However, there are some inconsistencies that impede the accurate determination of receptor distribution and need to be clarified. This paper aims to summarize results of the previously published studies observing the localization of opioid receptors in the rat CNS. Emphasis is placed on the comparison of results obtained by all available methods