BACKGROUND: Urtica dioica extract has been shown to play a protective role in the neurodegeneration associated with diabetes mellitus. OBJECTIVE: To verify the neuroprotective efficacy of nettle extract on pyramidal cell density in the CA3 hippocampal subfield following administration of Urtica dioica extract to young diabetic rats. DESIGN, TIME AND SETTING: A randomized, controlled, neurobiological study was performed at the Department of Histology and Embryology at the Gorgan University of Medical Sciences in Iran from 2006 to 2007. MATERIALS: Urtica dioica leaves were collected from a cultivated plant in the suburb of Gorgan (northern Iran) and taxonomically identified by the Department of Pharmacognosy, Mazandaran University of Medical Sciences. METHODS: A total of 20 male, albino, Wistar rats, aged 6–7 postnatal weeks, were randomly assigned to four groups: normal control, diabetic model, preventive, and treatment, with five rats in each group. Diabetes was induced by intraperitoneal injection of streptozotocin (80 mg/kg) in the diabetic and treatment groups. Rats from the preventive group received a hydroalcoholic extract of Urtica dioica (100 mg/kg per day) during the first 5 days, and then streptozotocin (80 mg/kg) was administered on day 6. One week following the streptozotocin injection, rats in the treatment group were intraperitoneally administered hydroalcoholic extract of Urtica dioica (100 mg/kg per day) for 4 weeks. MAIN OUTCOME MEASURES: Following administration of Urtica dioica extract, the dorsal hippocampal formation of the right cerebral hemispheres was stained with cresyl violet. Area densities of CA3 pyramidal cells were measured. RESULTS: The diabetic, preventive, and treatment groups exhibited reduced cell densities compared with the control group (P < 0.05). Moreover, densities of CA3 pyramidal cells in the treatment group were significantly reduced compared with the diabetic model group (P < 0.05). CONCLUSION: The Urtica dioica extract exhibited no significant neuroprotective benefits in diabetes-induced loss of pyramidal cells in the CA3 hippocampal subfields of young diabetic rats. BACKGROUND: Urtica dioica extract has been shown to play a protective role in the neurodegeneration associated with diabetes mellitus. OBJECTIVE: To verify the neuroprotective efficacy of nettle extract on pyramidal cell density in the CA3 hippocampal subfield following administration of Urtica dioica extract to young diabetic rats DESIGN, TIME AND SETTING: A randomized, controlled, neurobiological study was performed at the Department of Histology and Embryology at the Gorgan University of Medical Sciences in Iran from 2006 to 2007. MATERIALS: Urtica dioica leaves were collected from a cultivated plant in the suburb of Gorgan (northern Iran) and taxonomically identified by the Department of Pharmacognosy, Mazandaran University of Medical Sciences. METHODS: A total of 20 male, albino, Wistar rats, aged 6-7 postnatal weeks, were randomly assigned to four groups: normal control, diabetic model, preventive, and treatment, with five rats in each group. Diabetes was induced by intraperit Oneal injection of streptozotocin (80 mg / kg) in the diabetic and treatment groups. Rats from the preventive group received a hydroalcoholic extract of Urtica dioica (100 mg / kg per day) during the first 5 days, and then streptozotocin kg) was administered on day 6. One week following the streptozotocin injection, rats in the treatment group were intraperitoneally administered hydroalcoholic extract of Urtica dioica (100 mg / kg per day) for 4 weeks. MAIN OUTCOME MEASURES: Following administration of Urtica dioica extract , the dorsal hippocampal formation of the right cerebral hemispheres was stained with cresyl violet. Area densities of CA3 pyramidal cells were measured. RESULTS: The diabetic, preventive, and treatment groups exhibited reduced cell densities compared with the control group (P <0.05). Moreover, densities of CA3 pyramidal cells in the treatment group were significantly reduced compared with the diabetic model group (P <0.05). CONCLUSION: The Urtica dioica extract e xhibited no significant neuroprotective benefits in diabetes-induced loss of pyramidal cells in the CA3 hippocampal subfields of young diabetic rats.