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The effects of spermine and spermidine tetrahydrochloride on female Agus rat brain caudate nucleus homogenates. soluble acetylcholinesterase from the electric organ of Electrophorus electricus and acetylthiocholine iodide were studied. Measurements were made using an autoanalytical spectrophotometric method which measured the initial rate of reaction rapidly and accurately. Both polyamines intcrxtcd with the substrate. acetylthiocholine, causing an increase in the rate of its non-enzymatic hydrolysis. Slight inhibitory effects on acetylcholinesterase were also observed. Combined effect of thc polyamine on the substrate and the enzyme showed an inhibition at low and activation at high (above I mMI substrate concentrations Aci.TYL(.HOLiNFsTERAs~: (specific cholinesterase: acetylcholine acetylhydrolase: E C 3.1 .l.7), the enzyme responsible for the breakdown of acetylcholine, is modified in its activity by a large number of compounds (WOLF, 1965; CHANCEUX rt a/.. 1968; BELLEAU e t al.

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The present study was designed to investigate the effects of exposure to chronic predictable and unpredictable stress on neurobehavioral and biochemical responses in rats. Male Wistar rats (200-250g) were exposed to either chronic predictable stress (CPS) i.e. immobilization for 1 hour/day for 14 days or chronic unpredictable stress (CUS) i.e. daily a different, random, novel stressor sequence (immobilization stress for 1h, footshock, cold stress, overnight food and water deprivation and social isolation) for 14 days. Behavioral responses were assessed by the elevated plus maze (EPM) test and biochemical parameters, viz. malondialdehyde (MDA, a marker of oxidative stress) and stable NO metabolites (NOx, marker of nitrosative stress), were measured in brain homogenates of the rats. Exposure to chronic CPS resulted in adaptation to neurobehavioral suppression in the EPM (as observed after acute Restraint stress), which was not seen after CUS. These behavioral changes after CPS and CUS were closely paralleled by alterations in the levels of brain MDA and NOx. These results suggest that CPS and CUS results in differential modulation of the neurobehavioral profile and oxidative/nitrosative stress markers in the brain. Keywords:Chronic

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