Does long term treatment with amitriptyline alter the monoamine oxidase of rat brain?

Amitriptyline, at a concentration of 10(-5) M, inhibits the oxidative deamination of phenylethylamine, tyramine and tryptamine (by 40, 16, and 8 percent, respectively) by rat brain MAO. After the long term administration of amitryptyline, even at a dosage of 20 mg per kg body weight twice daily, there was no detectable influence on the biochemical properties of MAO. These findings indicate that the full antidepressive effect, which only appears after the first 3 weeks of long term treatment, cannot be caused by the inhibition of MAO.