Effects of cold exposure on behavioral and electrophysiological parameters related with hippocampal function in rats

Abstract

Aim: Behavioral and mental changes may occur in people exposed to cold stress by decreasing their work efficiency and their mental capacity while increasing the number of accidents on the job site. The goal of this study was to explore the effect of cold stress in spatial learning performance excitability and LTP.Materials and Methods: Three to four month old rats were randomly divided into four groups to form a control group and a cold stress group for each sex. The groups of cold stressed animals were placed in a cold room ambient temperature of 4°C for 2 h day. Adrenal glands and body weight (g) were recorded in control and stressed rats during the cold exposure. Spatial learning (acquisition phase) and memory (probe trial) were tested in the Morris water maze (MWM) immediately after daily exposure. Latency to locate the hidden platform, distance moved (DM), mean distance to platform, swim speed (SS) and time spent in the platform quadrant were compared between genders and treatments. Field potential recordings were made, under urethane anesthesia, from the dentate gyrus (DG) granule-cell layer, with stimulation of the medial perforant pathway 2 h after the probe trial. This study examined spatial memory as measured by MWM performance and hippocampal long-term potentiation (LTP) in the DG after exposure to cold in a repeated stress condition for 2 h/day for 5 days.Results: The cold-exposed female rats needed less time to find the hidden platform on day 1 (43.0 ± 13.9 s vs. 63.2 ± 13.2 s), day 2 (18.2 ± 8.4 s vs. 40.9 ± 12.2 s) and on day 4 (8.0 ± 2.1 s vs. 17.2 ± 7.0 s) while cold-exposed male rats showed a decreased escape latency (EL) on day 1 only (37.3 ± 12.5 s vs. 75.4 ± 13.1 s). Cold-exposed male rats spent less time in the target quadrant (30.08 ± 6.11%) than the control male rats (37.33 ± 8.89%). Two hour cold exposure decreased population spike (PS) potentiation during both induction (218.3 ± 21.6 vs. 304.5 ± 18.8%) and maintenance intervals (193.9 ± 24.5 vs. 276.6 ± 25.4%) in male rats. Meanwhile cold exposure did not affect the body weight (C: 221 ± 2.5 vs. S: 222 ± 1.7) but it impacts the adrenal gland relative weight (S: 27.1 ± 1.8 mg vs. C: 26.2 ± 1.4 mg).Conclusion: Overall, the results show that repeated cold exposure can selectively improve spatial learning in adult female rats, but impaired retention memory for platform location in male rats. It is possible that impaired LTP underlies some of the impaired retention memory caused by cold exposure in the male rats.

Effect of Cold Stress on Neurobehavioral and Physiological Parameters in Rats

“…As the first study, we demonstrated that spatial working memory appear to be not altered in female rats exposed to cold. While, our previous findings (El Marzouki et al, 2014) indicate that chronic intermittent cold stress procedure as administered in our laboratory lead to enhanced spatial learning in female rats and impaired memory retrieval in male rats.…”

“…The stress paradigm used in this study was chronic intermittent cold stress as described previously (El Marzouki et al, 2014). Rats in the cold stressed group were placed in their home cages in a cold room and exposed to 4 • C for 2 h, then returned to the housing facility for 5 consecutive days from 8:00 to 10:00 a.m. to avoid corticosterone circadian rhythm.…”

“…Although the cognitive and behavioral performance of stressed rodents depends on the type and intensity of stress, cold has been relatively little used as a stressor. Chronic intermittent cold exposure has been applied to induce stress in laboratory animals in order to investigate its effects on different aspects (Dorfman et al, 2009;Lapiz-Bluhm et al, 2009;Girotti et al, 2011;El Marzouki et al, 2014), these studies mainly focused on cognitive and electrophysiological parameters, coldinduced thermogenesis and metabolic responses to cold stress. To our knowledge, there is currently no study reporting the sexually dimorphic effect of intermittent cold stress on working memory and the development of anxiety-like behaviors in rats.…”

Adult Hippocampal Neurogenesis Can Be Enhanced by Cold Challenge Independently From Beigeing Effects

“…However, in the hippocampus, cold challenge is poorly understood, and controversial results have been reported. Cold challenge showed improvement in spatial learning scores and behavioral tests, but paradoxically with LTP impairment ( Elmarzouki et al, 2014 ). The purpose of this study was to investigate the relationship between cold challenge and changes in AHN and its related genes.…”

“…Correlation and interaction of peripheral adipose tissue with the brain is usually through cytokines from adipose tissue (adipokines; e.g., leptin), for example, the leptin and proopiomelanocortin neurons activated by insulin in the hypothalamus, as well as genetic inhibition of the agouti-related peptide neurons promote beige adipocyte biosynthesis ( Ruan et al, 2014 ; Dodd et al, 2015 ). In the study of behavioral- and electrophysiological parameter-linked hippocampal function, cold challenge was found to partially improve spatial learning scores but showed impaired long-term potentiation (LTP) ( Elmarzouki et al, 2014 ).…”