Alteration of histamine metabolism in the rat brain under influence of various antidepressive treatments.

Effects of acute and prolonged (14 days, twice daily) treatments with various antidepressants: tricyclic (AMI, DMI, DOX, IMI), atypical (IPR, CIT), MAO-inhibitors (NIA, PARG), as well as ECS (X 1 or X 10) on histamine (HI) levels, histidine decarboxylase (HD) and histamine-methyltransferase (HMT) activities in particular brain structures of the rat were investigated. Acute treatment with all the tested drugs had no effect on the studied histaminergic parameters. Prolonged treatment with tricyclic drugs (except DMI) decreased HI level in the cerebral cortex; AMI and IMI increased HD activity. Atypical drugs changed neither HI levels nor HD activities. MAO-inhibitors showed no consistent effects on both histaminergic parameters. ECS X 10 (once daily) increased significantly HD activity in the cerebral cortex at 1 and 24 h. None of the antidepressant treatments affected HMT activity. It is concluded that various antidepressant treatments did not uniformly affect the histaminergic system in the rat brain. The observed changes varied depending on the kind of treatment and the brain structure analysed.