AGN 2979 [3(3-methoxyphenyl)-3-(3-dimethylaminopropyl)-4, 4-dimethylpiperidine-2,6-dione]. An inhibitor of the activation of tryptophan hydroxylase.

AGN 2979 [3-(3-methoxyphenyl)-3-(3-dimethylaminopropyl)-4, 4-dimethylpiperidine-2,6-dione] blocked the increase in tryptophan hydroxylase activity that occurred when slices of brainstem were exposed to a depolarizing medium or to agents that mobilize intracellular pools of calcium, but it had no effect on the activity of enzyme prepared from slices of brainstem incubated in control medium. AGN 2979 also blocked the calcium-calmodulin-dependent activation of tryptophan hydroxylase that was seen when supernatant preparations of the enzyme were exposed to phosphorylating conditions but not the activation induced by calcium-dependent proteases that was triggered by millimolar calcium concentrations. An identical pattern of inhibition has been found with the antipsychotic drugs, haloperidol and fluphenazine [Boadle-Biber, Biochem. Pharmac. 31, 2495 (1982)]. The sensitivity to the same inhibitors of both the activation of tryptophan hydroxylase produced by pretreatment of brainstem slices and that induced by incubation of supernatant preparations of enzyme under phosphorylating conditions suggests involvement of a common mechanism of enzyme activation in response to these different treatments.