Assessment of Hippocampal Cell Death and Memory Deficits in Rats Following Neonatal Stress

Abstract

Objective: Neonatal stress (NS) has harmful effects on the hippocampal neurons of rat neonates. It has been reported to enhance neuronal cell death and impair memory behaviors. The researchers conducted this study in order to assess NS’s effects on hippocampal apoptosis and memory deficits in rat neonates’ hippocampus. Methods: Three groups of male Wistar rat neonates exposed to NS; rat neonates reared with 1 hour neonatal isolation (NI) for 8 consecutive days (P2-P9), rat neonates exposed to febrile seizure (FS) at day 10 (P10) and rat neonates reared with both NI plus FS (NI-FS). Control group was reared normally. Novel object recognition test (NORT) carried out to evaluate the effects of NI, FS and NI-FS on memory deficits. At day 22 (P22), Terminal deoxynucleotidyl transferase- mediated dUTP nick end labeling (TUNEL) assay was done. Results: NORT demonstrated that rat neonates exposed to NI-FS had short-term and long-term memory deficits (P<0.01 and P<0.001). Rat neonates experienced NI had long-term memory deficits (P<0.05). TUNEL assay results showed that NI-FS increased the count of hippocampal apoptotic neurons in Cornu Ammonis 1 (CA1), Cornu Ammonis 3 (CA3) and dentate gyrus (DG) subfields (P<0.001, P<0.001 and P<0.001). Also, NI increased the count of hippocampal TUNEL positive cells in CA3 and DG subfields (P<0.05 and P<0.01). In addition, FS increased the count of hippocampal apoptotic neurons in DG subfield (P<0.05). Conclusion: The present results showed that NS exerted apoptotic effect and induced memory deficits in the hippocampus of rat neonate.