Exposure to chronic constant light impairs spatial memory and influences long-term depression in rats.
Exposure to chronic constant light (CCL) influences circadian rhythms and evokes stress. Since hippocampus is sensitive to stress, which facilitates long-term depression (LTD) in the hippocampal CA1 area, we examined whether CCL exposure influenced hippocampus-dependent spatial memory and synaptic plasticity in Wistar rats. Here we report that CCL exposure (3 weeks) disrupted 24-h cycle of locomotion activity in open field test. These rats showed shorter escape latency during initial phase of spatial learning but impaired hippocampus-dependent spatial memory without affecting the visual platform learning task in Morris water maze (MWM) compared with control rats. This effect may be due to stress adaptation as reflected by reduced thigmotaxis and anxiety-like behaviors in CCL rats. Moreover, in CA1 area of the hippocampal slices, CCL rats failed to show LTD by low frequency stimulation (LFS, 900 pulses, 1 Hz), while showed decreased short-term depression compared with control rats indicating the induction of LTD was influenced by CCL exposure. Furthermore, additional acute stress enabled LFS to induce LTD in control rats but not in CCL rats. Thus, these results suggested that CCL exposure impaired spatial memory and influenced hippocampal LTD, which may be due to stress adaptation.
Ma
Wen-Pei
WP
Department of Biology, Yunnan University, Kunming 650021, PR China.
Cao
Jun
J
Tian
Meng
M
Cui
Ming-Hu
MH
Han
Hui-Li
HL
Yang
Yue-Xiong
YX
Xu
Lin
L
D000222:Adaptation, Physiological / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D021081:Chronobiology Disorders / Q000209:etiology / Q000503:physiopathology; D002940:Circadian Rhythm / Q000502:physiology / Q000528:radiation effects; D004558:Electric Stimulation; D006624:Hippocampus / Q000503:physiopathology*; D008027:Light / Q000009:adverse effects*; D036881:Long-Term Synaptic Depression / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000502:physiology / Q000528:radiation effects; D008569:Memory Disorders / Q000209:etiology / Q000503:physiopathology*; D009043:Motor Activity / Q000502:physiology / Q000528:radiation effects; D009924:Organ Culture Techniques; D010775:Photic Stimulation / Q000009:adverse effects*; D051381:Rats; D017208:Rats, Wistar; D013315:Stress, Psychological / Q000209:etiology / Q000503:physiopathology*