EFFECTS OF ANESTHESIA ON POLYAMINE METABOLISM AND WATER-CONTENT IN THE RAT-BRAIN

Because variances have been noted in brain putrescine levels of anesth etized rats (control, SHAM-operated), we investigated the effects of s everal anesthetics on polyamine metabolism and water content in the ad ult rat brain. Short duration (5 min) anesthesia was studied in three groups: ketamine:xylazine [KX; 40 and 8 mg/kg, respectively, intraperi toneal injection (IP)], urethane (UR; 1.5 g/kg, IP), and isoflurane (I F, initially 3.5% in 100% O-2, followed by a maintenance dose of 2.5% IF in 100% O-2). Effects of IF at longer duration (30 min) were also s tudied because this paradigm is often used in our laboratory. Control rats received no anesthesia (NA). Following decapitation, tissue sampl es were obtained from 3 bilateral brain regions: parietal cortex, moto r area (CPm); parietal cortex, somatosensory area (CPs); and the pyrif orm cortex (CPF). The polyamines, spermidine and spermine, and their p recursor, putrescine, were quantified by HPLC-fluorometric detection a nd brain water content was determined by wet-to-dry weight measures. K X decreased putrescine (54%) and spermidine (20%) in the CPs, increase d spermine (24%) in the CPF, and increased water content in all brain regions. UR decreased putrescine (51%) and slightly increased water co ntent (0.7%) in the CPF. Short duration IF decreased putrescine and sp ermidine in all brain regions; decreased spermine in the CPm, and incr eased water content in the CPF (0.8%). In contrast, longer duration IF increased putrescine (181%) and spermidine (23%) in the CPm, with no change in water content. Anesthetics produce region-specific changes i n putrescine, polyamines, and water content in the rat brain which cou ld contribute to the experimental variability.