Role of thiamine metabolism in the central nervous system. II. Effects of various agents on thiamine triphosphatase activity in rat brain.

The effects of various agents on the activity of brain thiamine triphosphatase (TTPase) in vivo and in vitro were studied. Thiamine deficiency caused a significant increase in soluble TTPase activity and a decrease in membrane-associated TTPase activity. Insulin and a fasting state did not affect these enzyme activities. DL-Methamphetamine (10mg/kg i.p.) increased the activity of the soluble TTPase, whereas reserpine (2.5 mg/kg i.p.) caused no change in the enzyme activities. A single injection of chlopromazine (25 mg/kg s.c.) had no effect on the microsomal or soluble TTPase activities, but repeated injections reduced the activity of the microsomal enzyme. The effects of various neuroactive agents on microsomal TTPase activity were examined in vitro. Among the drugs tested, only chlorpromazine caused marked inhibition of the enzyme activity.