NEUROETHOLOGIC DIFFERENCES IN SLEEP-DEPRIVATION INDUCED BY THE SINGLE-PLATFORM AND MULTIPLE-PLATFORM METHODS

It has been proposed that the multiple-platform method (MP) for desync hronized sleep (DS) deprivation eliminates the stress induced by socia l isolation and by the restriction of locomotion in the single-platfor m (SP) method. MP, however, induces a higher increase in plasma cortic osterone and ACTH levels than SP. Since deprivation is of heuristic va lue to identify the functional role of this state of sleep, the object ive of the present study was to determine the behavioral differences e xhibited by rats during sleep deprivation induced by these two methods . All behavioral patterns exhibited by a group of 7 albino male Wistar rats submitted to 4 days of sleep deprivation by the MP method (15 pl atforms, spaced 150 mm apart) and by 7 other rats submitted to sleep d eprivation by the SP method were recorded in order to elaborate an eth ogram, The behavioral patterns were quantitated in 10 replications by naive observers using other groups of 7 rats each submitted to the sam e deprivation schedule. Each quantification session lasted 35 min and the behavioral patterns presented by each rat over a period of 5 min w ere counted. The results obtained were: a) rats submitted to the MP me thod changed platforms at a mean rate of 2.62 +/- 1.17 platforms h(-1) animal(-1); b) the number of episodes of noninteractive waking patter ns for the MP animals was significantly higher than that for SP animal s (1077 vs 768); c) additional episodes of waking patterns (26.9 +/- 1 8.9 episodes/session) were promoted by social interaction in MP animal s; d) the cumulative number of sleep episodes observed in the MP test (311)was significantly lower (chi-square test, 1 d.f., P<0.05) than th at observed in the SP test (534); e) rats submitted to the MP test did not show the well-known increase in ambulatory activity observed afte r the end of the SP test; f) comparison of 6 MP and 6 SP rats showed a significantly shorter latency to the onset of DS in MP rats (7.8 +/- 4.3 and 29.0 +/- 25.0 min, respectively; Student t-test, P<0.05), We c onclude that the social interaction occurring in the MP test generates additional stress since it increases the time of forced wakefulness a nd reduces the time of rest promoted by synchronized sleep.