CHANGES IN MONOAMINES AND THEIR METABOLITE CONCENTRATIONS IN REM SLEEP-DEPRIVED RAT FOREBRAIN NUCLEI

Rapid eye movement sleep deprivation (REMSD) is a potent stressor in r ats. Behavioral abnormalities such as passive and active avoidance, lo comotor activity, problem solving, sensory information processing, and the development of adaptive copping strategy in response to repeated stress are among the earliest obvious symptoms of REMSD, the mechanism for which remain largely unknown. The aim of this study was to determ ine whether 96 h of REMSD causes changes in monoamine neurotransmitter s concentrations in rat forebrain regions (frontal cortex, FC; parieta l cortex, PC, and striatum) that are involved in mediating higher brai n functions such as attentional mechanisms, sensory information proces sing, and locomotor activity, which are severely affected in REMSD con ditions. Rats were subjected to 96 h of REMSD using inverted flower po t water tank technique. To account for the stress associated with wate r tanks, a tank control group (TC) was included where the animals coul d reside comfortably on a large pedestal in the water tank. Regional b rain concentrations of norepinephrine (NE), dopamine (DA), dihydroxyph enyacetic acid (DOPAC), L-3,4-dihydroxyphenylalanine (L-DOPA), homovan illic acid (HVA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleaceti c acid (HIAA) were determined by electrochemical detection using high- performance liquid chromatography. The concentrations of serotonin and its metabolite, HIAA, was reduced in the frontal and parietal cortexe s of REMSD rats compared with TC or cage control (CC) group. NE, DA, D OPAC, and HVA concentrations in FC and PC of REMSD animals were remain ed unchanged compared with TC or CC rats. A significant increase in th e concentrations of DA metabolites was observed in the striatum of REM SD rats when compared with CC and TC rats. There was a 29 and 31% incr ease in the concentration of striatal DA in REMSD group compared to th e TC and CC groups, respectively; however, these percentages were not statistically different. Striatal NE, 5-HT, and HIAA concentrations we re not significantly different among the three groups. These results s uggest that 96 h of REMSD alters dopaminergic and serotonergic systems in different locations in rat brain. The effect of REMSD on the serot onergic systems are localized in the cerebral cortex, whereas dopamine rgic metabolism is increased in the striatum.