Increases in avoidance responding produced by REM sleep deprivation or serotonin depletion are reversed by administration of 5-hydroxytryptophan.
Our objective was to directly compare the effects of rapid eye movement (REM) sleep deprivation (REMSD) and serotonin 5-hydroxytryptamine (5-HT) depletion on free-operant avoidance behavior in rats. These experiments were designed to determine if declining 5-HT levels observed during REMSD might mediate the increases in avoidance responding observed in REM sleep deprived rats. Rats were trained on a free-operant avoidance task. Following training, the animals were assigned to one of three sleep conditions (REMSD, tank control, or cage control). Animals in each sleep condition were exposed to four 5-HT manipulations: (a) saline plus saline; (b) p-chlorophenylalanine (PCPA) plus saline; (c) saline plus 5-hydroxytryptophan (5-HTP) and (d) PCPA plus 5-HTP. Both REMSD and 5-HT depletion via PCPA resulted in an increase in avoidance responding that was reversed by administration of 5-HTP. REMSD and 5-HT depletion via PCPA resulted in increased avoidance efficiency and were reversed by 5-HTP administration, but only changes following PCPA injection were statistically significant. Decreases in 5-HT levels that occur during REMSD likely mediate increases in avoidance responding.
Smith
Randy L
RL
Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37203, USA.
Kennedy
Craig H
CH
D006916:5-Hydroxytryptophan / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects* / Q000502:physiology; D001522:Behavior, Animal / Q000187:drug effects*; D003216:Conditioning, Operant / Q000187:drug effects; D004338:Drug Combinations; D010134:Fenclonine / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000172:deficiency / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D012892:Sleep Deprivation / Q000188:drug therapy / Q000503:physiopathology*
D004338:Drug Combinations; D012702:Serotonin Antagonists; D012701:Serotonin; D006916:5-Hydroxytryptophan; D010134:Fenclonine