Salivary monoamine oxidase A and B inhibitory activities correlate with stress

MAO A and B inhibitory activities were determined, for the first time, in saliva samples. Saliva was collected on 4 occasions from 11 normal subjects (students) before and after delivering an important assessed oral presentation, a naturalistic stress inducing procedure. The first sample was collected 30 minutes before the presentation and 3 more within 40 minutes of finishing the presentation. At each collection a mood adjective checklist was completed. Mean MAO A inhibitory activity correlated with mean MAO B inhibitory activity (r = 0.872, p < 0.001, n = 11). Within subject analysis revealed a positive correlation between MAO A and B inhibitory activity and stress (r = 0.400, p < 0.01, n = 44 and r = 0.255, NS, n = 38 respectively). Mean MAO A and B inhibitory activity correlated with mean stress (r = 0.535, NS, n = 11 and r = 0.673, p < 0.05, n = 11 respectively). Peak MAO A and B inhibitory activities correlated with peak stress (r = 0.636, p < 0.05, n = 11 and r = 0.754, p < 0.01, n = 11, respectively). Salivary MAO A and B inhibitory activities were independent of salivary flow rate. We conclude that measurement of MAO A and B inhibitory activities in saliva is preferable to traditional urinary measures as sampling is less invasive and also supports a clear relationship to stress in normal individuals.