Clorgyline effect on pineal melatonin biosynthesis in Roman high- and low-avoidance rats.

Pineal melatonin and related indoles levels were higher in Roman high- than in Roman low-avoidance rats, while 5-HIAA/5-HT ratio, as an index of MAO activity was higher in low- than in high-avoidance rats. Clorgyline stimulated pineal melatonin biosynthesis in both lines of rats. However, melatonin and N-acetylserotonin levels remained higher and 5-HIAA levels remained lower in the high avoidance rats treated with low dose (0.5 mg/kg) while treatment with 1.0 mg/kg of clorgyline eliminated the differences in melatonin production between high- and low-avoidance rats.