Platelet monoamine oxidase activity in female migraine patients. Platelet monoamine oxidase activity (MAO) in a group (n = 17) of white, female migraineurs during an acute migraine attack was similar to both the values obtained for the same group of patients two to three weeks after the headache episode (pain-free period) and to the results obtained for a group (n = 18) of sex and race-matched, age-comparable, drug-free healthy volunteers (blind study; substrate p-tyramine, 38.7 +/- 5.7, 41.9 +/- 8.8 and 43.0 +/- 3.4 or p-methoxybenzylamine, 178.9 +/- 11.3, 177.2 +/- 6.9 and 181.0 +/- 9.7 nmole/hr/10(9) platelets +/- SD respectively). With each patient serving as its own control, MAO activity during the migraine episode and when pain-free failed to show a significant trend. Neither a number of other medical conditions nor the use of several medications appeared to significantly influence our results. The present work, while dealing only with a small but well defined patient population, argues against the possible usefulness of platelet MAO activity as a biological marker for migraine headaches. 