Morphine alters the structure of neurons in the nucleus accumbens and neocortex of rats

Rats were given repeated injections of 10 mg/kg of morphine and were then l eft undisturbed for 24-25 days before their brains were processed for Golgi -Cox staining. Prior exposure to morphine decreased the complexity of dendr itic branching and the number of dendritic spines on medium spiny neurons i n the shell of the nucleus accumbens and on pyramidal cells in the prefront al and parietal cortex. It is suggested that some of the long-term behavior al consequences of repeated exposure to morphine may be due to its ability to reorganize patterns of synaptic connectivity in the forebrain. (C) 1999 Wiley-Liss, Inc.