Effects of chronic treatment with typical and atypical antipsychotic drugson the rat striatum

Human MRT studies have demonstrated that treatment with typical antipsychot ics may increase the volume of the caudate nucleus while clozapine treatmen t is associated with either no change or a reversal of the previous volume increase. In this study four groups of seven rats were treated for 8 months with either the typical antipsychotic haloperidol, the atypical antipsycho tic clozapine, the D-2/D-3 receptor antagonist raclopride, or vehicle (plai n drinking water). Striatal sections were prepared using D-1-like and D-2- like receptor ligand autoradiography. Images(46 sections per rat, per ligan d) were digitized and the area of the striatum was measured on each section . Rats treated with haloperidol did not have a larger mean striatum area th an the control group on either D-1- or D-2-like ligand autoradiograms. Usin g the D-2-like ligand autoradiograms, the clozapine treated animals had a s maller mean striatum area than the control group. Mean left striatum area w as larger than mean right striatum area in each treatment group and in the control group. In contrast to the MRI findings reported in schizophrenia, t he area of the striatum was not increased in rats treated with typical anti psychotic agents, but the clozapine-associated area reduction may parallel the clinical studies.