Decreased density of I2-imidazoline receptors in the postmortem brain of heroin addicts.

The aim of this study was to quantitate imidazoline receptors in postmortem brains of heroin addicts who died of an opiate overdose. The density of I2-imidazoline receptors ([3H]idazoxan binding in the presence of adrenaline) and the immunoreactivity of the related 29/30 kDa imidazoline receptor protein were decreased (39% and 28%, respectively) in the frontal cortex. The density of brain I2-imidazoline receptors was also decreased in heroin-dependent rats (27%). This novel finding indicates that opiate addiction induces down-regulation of I2-imidazoline receptors in astrocytes, and presumably down-regulation of the functions associated with these receptors.