RESUMO
BACKGROUND: Cholecystokinin (CCK) has roles in learning and memory, but the cellular mechanism is poorly understood. This study investigated the effect of CCK on spatial learning and memory, neuronal proliferation and apoptosis in the hippocampus in rats. MATERIALS AND METHODS: Experimental groups were control and CCK. The rats received CKK octapeptide sulfated (CCK-8S, 1.6 µg/kg, i.p.) for 14 days. Spatial learning and memory were tested by Morris water maze and finally immunohistochemical study was performed; neurogenesis by Ki-67 method and apoptosis by Terminal deoxynucleotidyl transferase mediated dUTP Nick End Labeling (TUNEL) assay in hippocampal dentate gyrus (DG). RESULTS: Cholecystokinin increased Ki-67 positive cells and reduced TUNEL positive cells in the granular layer of hippocampal DG. CCK failed to have a significant effect on spatial learning and memory. CONCLUSION: Results indicate neuroprotective and proliferative effects of CCK in the hippocampus; however, other factors are probably involved until the newly born neurons achieve necessary integrity for behavioral changes.
RESUMO
BACKGROUND: Alzheimer's disease (AD) is a prevalent disorder with severe learning and memory defects. Because it has been demonstrated that erythropoietin (EPO) has positive effects on the central nervous system, the aim of this study was to evaluate the effect of EPO on neuronal proliferation in dentate gyrus of hippocampal formation in a well-defined model for AD. MATERIALS AND METHODS: A rat model of sporadic dementia of Alzheimer's type was established by a bilateral intracerebroventricular injection of streptozotocin (ICV-STZ). Impairment of learning and memory was confirmed 2 weeks after ICV-STZ injection by passive avoidance learning test and then rats were divided into fourgroups:Control, control-EPO, Alzheimer and Alzheimer-EPO. EPO was injected intraperitoneally every other day with a dose of 5000 IU/kg and, finally, the rats were anesthetized and decapitated for immunohistochemical study and neurogenesis investigation (by Ki67 method) in dentate gyrus of hippocampal formation. RESULTS: The results driven from the histological study showed that EPO significantly increases neuronal proliferation in dentate gyrus of hippocampus in the Alzheimer-EPO group compared with the control, control-EPO and Alzheimer groups; however, there were no differences between the other groups. CONCLUSION: Our results show that even though EPO in intact animals doesnot change neurogenesis in dentate gyrus, it can nonetheless significantly increase neurogenesis if there is an underlying disorder like neurodegenerative diseases.
