The effect of the calcium antagonist verapamil on NADPH‐diaphorase activity was studied in the frontal cortex of rats with lesioned nucleus basalis magnocellularis (NBM). Treatment with verapamil (5 mg/kg/12h ip) started 24 h after NBM lesions and lasted 8 days. Animals were sacrificed on day 21 after NBM‐lesions. There were no significant differences between control, saline‐ and verapamil‐treated NBM‐lesioned rats in the total number of neurons expressing NADPH‐diaphorase. However, the number of neurons which show loss of enzymatic reaction in their processes was significantly higher in saline‐treated NBM‐lesioned rats. This may relate to incipient neurodegeneration in these neurons. The obtained reactive decrease of NADPH‐diaphorase staining was abolished by verapamil treatment, which suggests a significant neuroprotective effect of this calcium antagonist.