Alteration of cerebral neurotransmitter receptor function by exposure of rats to manganese

Adult male rats were treated on 15 successive days with i.p. injection of manganese chloride at 10 or 15 mg/kg body weight. 24 h after the last dose, the binding of the dopaminergic antagonist [3H]spiroperidol to striatal membranes was elevated significantly. At the lower dose, no other high-affinity binding site measured was altered. However, at the 15 mg/kg body weight dose, cerebellar GABA, frontal cortical serotonin, and striatal muscarinic binding were all depressed. Neither dose level altered striatal levels of enkephalin, substance P, dopamine, serotonin, or dihydroxyphenylacetic acid (DOPAC). Receptor binding measurements may be a sensitive means of detecting disturbances of specific neural circuits.