Morphological effects of chronic haloperidol administration on the postnatal development of the striatum.

The aim of this paper is to describe the morphological changes induced in the striatum after the administration of haloperidol during the first postnatal month, a period in which a lack of tolerance to treatment with neuroleptics has been reported. At the end of the treatment several morphological parameters were evaluated including neuron size and density and the synaptic profile areas of cross-sectioned dendrites and axon terminals. The results evidenced a loss of the smallest dendritic profiles without the rest of the parameters examined being affected. This response differs from the one observed in the adult rat striatum that does develop tolerance to haloperidol. It seems to more closely correspond to the changes found in the prefrontal cortex, a region that does not develop tolerance after chronic treatment with neuroleptics.