The present study was undertaken to determine whether or not STH influences anesthesia and brain 5-HT increasing actions of pentobarbital and if such is the case does adrenalectomy inhibit the effect of STH. Male Wistar rats were adrenalectomized or sham-operated and injected with STH (growth hormone 2mg/kg per day, i. p.) or its solvent everyday for I week after a postoperative interval of I week. These rats were given a normal diet and 1% saline_??_5% glucose solution. Animals were injected with pentobarbital (50mg/kg i. p.) 18hr after the last injection of STH, and 50% of each group were used to determine the anesthetic effect. The other 50% were decapitated at time intervals of 0min, 15min and 30min after pentobarbital treatment, to determine 5-HT content in the brain. Results are as follows; 1) Chronic administration of STH enhanced “pentobarbital-anesthesia”, although there was no such effect in the adrenalectomized rats. 2) STH administration to adrenalectomized rats induced marked increase of 5-HT in the brain after pentobarbital, although the same treatment for sham-operated rats did not influence the increase as described above.
