Heroin-induced neuronal activation in rat brain assessed by functional MRI

The present study demonstrates the application of fMRI technology to neurop harmacology and the interaction of drug/receptor in the rat brain. Specific ally, we have observed two different types of fMRI signal changes induced b y acute i.v. heroin administration in rat brains under conditions of sponta neous and artificial respiration. Under spontaneous respiration, a global d ecrease in fMRI signal was observed; under artificial respiration, a region -specific increase in fMRI signal was identified and the activation sites a re consistent with the distribution of opiate mu-receptors in rat brain as previously reported by autoradiography. Both heroin-induced fMRI signal cha nges were suppressed by pretreatment of naloxone, an opiate mu-receptor ant agonist, and reversed by injection of naloxone following heroin infusion. T hese results suggest that fMRI has specific advantages in spatial and tempo ral resolution for studies of neuropharmacology and drugs of abuse. NeuroRe port 11:1085-1092 (C) 2000 Lippincott Williams & Wilkins.