Depression-like state in maternal rats induced by repeated separation of pups is accompanied by a decrease of cell proliferation and an increase of apoptosis in the hippocampus.
Stressful experiences, such as an unsatisfactory mother-infant relationship after delivery, can induce depressive disorders, and it is well-known that stressors impair memory function. The hippocampus plays a crucial role in memory processes. In the present study, we determined whether a depressed-like state induced by repeated separation of pups affects the memory capability of the maternal rats. We also determined the effects of repeated separation from pups on cell proliferation, apoptosis, and serotonin expression in the brains of maternal rats. In the present results, the immobility time in the forced swim test was increased and the climbing time was decreased in the mothers separated from their pups. The latency in the step-down avoidance task was increased in the mothers separated from their pups. Also, the expressions of serotonin (5-hydroxytryptamine) and tryptophan hydroxylase in the dorsal raphe were decreased in the mothers separated from their pups. The number of Ki-67-positive cells was decreased, while the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells in the hippocampal dentate gyrus was increased in the mothers separated from their pups. Based on the present results, it is suggested that separation of pups might induce a depressed-like state in the maternal rats with reduced cell proliferation and increased apoptosis in the hippocampus, resulting in memory impairment of maternal rats.
Sung
Yun-Hee
YH
Department of Physiology, College of Medicine, Kyung Hee University, #1 Hoigi-dong, Dongdaemoon-gu, Seoul 130-701, Republic of Korea.
Shin
Mal-Soon
MS
Cho
Sehyung
S
Baik
Hyung-Hwan
HH
Jin
Byung-Kwan
BK
Chang
Hyun-Kyung
HK
Lee
Eun-Kyu
EK
Kim
Chang-Ju
CJ
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D049109:Cell Proliferation; D018891:Dentate Gyrus / Q000503:physiopathology; D003866:Depressive Disorder / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D006624:Hippocampus / Q000503:physiopathology*; D020287:In Situ Nick-End Labeling; D019394:Ki-67 Antigen / Q000378:metabolism; D008426:Maternal Deprivation; D008568:Memory / Q000502:physiology; D008569:Memory Disorders / Q000503:physiopathology; D009035:Mothers; D011897:Random Allocation; D011903:Raphe Nuclei / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000378:metabolism
D019394:Ki-67 Antigen; D012701:Serotonin; D014365:Tryptophan Hydroxylase