We investigated changes in the brain distribution of (-)-[(125)I]-m-iodovesamicol [(-)-[(125)I]mIV] in cholinergic denervation rats produced by a unilateral lesion of the nucleus basalis magnocellularis (NBM). Dual-tracer ex vivo autoradiographic analysis using (-)-[(125)I]mIV and [(99m)Tc]HMPAO was conducted to the effect of regional cerebral perfusion on the brain distribution of (-)-[(125)I]mIV in a unilateral NBM-lesioned rat. (-)-[(125)I]mIV binding in the ipsilateral cortex to the lesion significantly reduced by 10.4 %, compared with that in the contralateral cortex, while (-)-[(125)I]mIV binding in the ipsilateral caudate putamen, hippocampus and thalamus did not change. The rate of reduction in the (-)-[(125)I]mIV binding (10.4 %) was significantly higher than that of [(99m)Tc]HMPAO accumulation (4.0%) in the ipsilateral cortex to the lesion (P < 0.01). These results suggested that radioiodinated (-)-mIV may be useful in the study of dementia characterized by degeneration of the cholinergic neurotransmitter system, such as Alzheimer's disease.