/ eh08 2484 Mp 249 Wednesday Jan 15 08:34 AM EL–PB (v. 61, No. 2) 2484 249 Physiology & Behavior, Vol. 61, No. 2, pp. 249–256, 1997 Copyright  1997 Elsevier Science Inc. Printed in the USA. All rights reserved 0031-9384/97 $17.00 / .00 PII S0031-9384( 96 ) 00363-0 Sleep Deprivation by the ‘‘Flower Pot’’ Technique and Spatial Reference Memory BRADLEY D. YOUNGBLOOD, JUN ZHOU, GENNADY N. SMAGIN, DONNA H. RYAN AND RUTH B. S. HARRIS 1 Department of Neuroscience, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808 USA Received 8 August 1996 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 paradox- ical, 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 condi- tions. Copyright  1997 Elsevier Science Inc. Paradoxical sleep deprivation Reference memory Rats Catecholamines Serotonin 1 To whom requests for reprints should be addressed. E-mail: Harrisrb@mhs.pbrc.edu PARADOXICAL, or rapid eye movement (REM), sleep depri- vation ( SD ) disrupts a number of physiological systems resulting in hyperphagia (4,10), weight loss (10), hypothermia (2), and impaired immune function (8). In addition to its physiological effects, sleep deprivation impairs cognitive function. Human sub- jects deprived of sleep show increased irritability, aggressive- ness, and restlessness with reduced alertness, discrimination, and learning recall ( 18 ) . Impairment of vigilance and mood have also been reported for subjects when the duration of sleep is kept constant but the sleep-wake cycle is shifted (29). In rats, sleep deprivation results in a variety of behavioral changes. SD rats show increased aggression, and locomotor and exploratory activity, but decreased emotionality, less fear, and greater sensitivity to environmental stimuli than controls ( 1,14,21,26 ) . SD immediately following training sessions has been reported to retard bar-press acquisition (24) and to prevent assimilation of nonreward conditions that normally facilitate ex- tinction of bar-pressing (23) or conditioned taste aversion (33). However, REM sleep is not required for assimilation of position habit in a Y maze; therefore, Pearlman and Becker ( 24 ) proposed that posttraining REM sleep was required for consolidation of learning complex, but not simple, tasks. Investigation of the effects of SD prior to training sessions for acquisition and retention paradigms has provided mixed results, and the relationship between SD and task complexity no longer appears to apply. SD prior to training has been reported to have no effect on acquisition of a passive-avoidance task, but to impair retention of the response when tested as early as 5 min after training ( 6,12,28 ) . Albert et al. ( 1 ) reported that SD had no effect on either acquisition or retention of a one-way avoidance re- sponse, whereas Stern (28) found that SD impaired the learning of a similar type of avoidance task and van Hulzen and Coenen (31) found a slowing of acquisition, but no change in retention of a 2-way active-avoidance task. Stern (28) also reported im- paired learning of a single alternation-discrimination task that had sucrose solution as the reward for food-deprived SD rats. Oniani (22) suggested that impaired acquisition and retention of avoidance tasks was confounded by the reduction in fear and increase in exploratory behavior of SD rats. However, this does not account for the failure to learn food-rewarded discrimination (28). Therefore, SD appears to cause a general disruption of acquisition and retention that is not task specific. Changes in central function that cause behavioral deficits in SD rats have not been clarified. Hartmann and Stern (13) re-