Elsevier

Physiology & Behavior

Volume 61, Issue 2, February 1997, Pages 249-256
Physiology & Behavior

Sleep Deprivation by the “Flower Pot” Technique and Spatial Reference Memory

https://doi.org/10.1016/S0031-9384(96)00363-0Get rights and content

Abstract

Youngblood, B. D., J. Zhou, G. N. Smagin, D. H. Ryan and R. B. S. Harris. Sleep deprivation by the “flower pot” technique and spatial reference memory. Physiol Behav 61(2) 249–256, 1997.—This study investigated whether paradoxical, or rapid eye movement (REM), sleep deprivation (SD) affected spatial memory. SD was induced in male Wistar rats by housing them on small platforms over water. They fell into the water if they lost muscle tone. Controls were either housed in tanks with large platforms (TC) or in normal cages (CC). All rats had free access to food and water. Each day they were tested in a place-learning set task using a Morris water maze. The rats were released from 6 different starting points (sets) and allowed 2 min to find a submerged platform. Two trials were conducted from each starting point. SD caused a significant decrement in performance in Trial 1 from Day 2. By Day 4, when distance swum to find the platform was plotted against set, area under the curve was doubled in SD compared to that in TC and CC rats, indicating a significant impairment in reference spatial memory. There was no consistent effect on working memory, indicated by Trial 2. SD caused weight loss and increased serum corticosterone compared to that in CC rats. There were no differences in concentrations of hypothalamic, hippocampal, or cortical catecholamines or their metabolites. Serotonin metabolism was elevated in the hypothalamus and hippocampus in SD rats. These results indicate that SD induced in rats housed on small platforms causes a substantial impairment of reference memory. The memory deficit may not be specific to SD because the rats are physically stressed and lose some nonREM sleep when housed in these conditions.

Section snippets

Methods

In a pilot study (data not reported here), 400-g rats were housed in cages with platforms of surface area 33 cm2 for SD and 154 cm2 for TC rats. Both TC and SD rats lost significant amounts of weight during the 5 days of the experiment, and 1 SD rat died on Day 4. In addition, TC rats exhibited increased locomotor activity by swimming faster than either CC or SD rats, and also showed partial impairment of reference memory, compared with CC rats, suggesting that the ratio of rat size to platform

Results

Initial body weights, weight change, and adrenal weights of the rats are given in Table 1. SD rats lost weight, TC rats maintained weight, and CC rats gained weight during the 4-day experiment. The weight change of SD rats was significantly different from that of CC or TC rats [F(2,20) = 56, p < 0.0001]. Treatment had no significant effect on adrenal gland weight and none of the rats had visually obvious gastric ulcers. Serum corticosterone was significantly increased in SD rats compared with

Discussion

This study demonstrates that 4 days of SD stress causes a substantial impairment of reference memory, but has no effect on working memory in rats. These results agree with those of Stern [28], who demonstrated that SD rats were able to retain a passive-avoidance behavior when tested 5 s following a single training session, but showed a deterioration of retention when tested 5 min after training. The time intervals used in this study were 30 s between each trial and approximately 25 min between

Acknowledgements

This work was supported by the U.S. Army Medical Research and Development Commmand grant number DAMD 17-92-V-2009.

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