A new computer-assisted image analysis procedure was developed for the analysis of striatal compartments of the rats visualized in this case by means of c-fos immunocytochemistry after morphine and/or d-amphetamine treatments. In particular it has been shown that d-amphetamine can induce an activation of the c-fos early gene in various subregions of the neostriatum and that morphine treatment can antagonize this activation. A different pattern of morphine antagonistic action could be detected at the rostral versus the caudal striatal level. In fact, at the rostral level the morphine antagonistic action was very marked only in the dorsomedial striatum, while at the caudal level the morphine antagonistic action was marked in all subregions. The developed computer-assisted procedure can detect differences in the pattern of distribution of profiles present in a certain neuroanatomical area. Therefore, this procedure may represent a powerful tool to study integrative functional compartments in the neostriatum. In the present study high level integrative compartments appear to be created by D1/mu-opiate receptor interactions especially within the classical patch system.