Differential responses of noradrenaline and dopamine neurons in the mouse forebrain induced by continuous parenteral infusion of haloperidol.

We examined the effect of haloperidol treatment on catecholamine (CA) levels in the forebrain of mice. Haloperidol (672 micrograms) or a vehicle lactate solution was continuously infused by an osmotic minipump implanted in the peritoneal cavity over a period of 1 week. Following sacrifice, several forebrain regions were studied for CAs either by fluorescence histochemistry or by biochemical assay. Histochemically, a remarkable reduction in the fluorescence intensity and the density of nerve fibers was observed. The largest reductions occurred in the medial prefrontal and parietal cortices, with moderate reductions in the anterior cingulate cortex and stria terminalis, with only a slight reduction in the striatum, nucleus accumbens and olfactory tubercle. Biochemical measurements were performed in the following four regions: the medial prefrontal, anterior cingulate, parietal cortex and striatum. The largest reduction of the dopamine (DA) levels were found in the medial prefrontal cortex, with moderate reductions in the anterior cingulate cortex and striatum. Noradrenaline (NA) levels on the other hand, were decreased in all of the above-mentioned four regions, being largest in the parietal cortex. These results suggest that the pharmacological actions of haloperidol involve NAergic as well as DAergic systems in a region-specific manner.