Effect of indomethacin and meloxicam on monoamine levels in selected tissues of rats

The effects of i.p. injection of indomethacine [25 mg/kg body wt] or meloxicam [4 mg/kg body wt] on the levels of dopamine [DA], norepinephrine [NE], serotonin [5-HT] and 5-hydroxyindolacetic acid [5-HIAA] were examined in plasma, different brain regions, liver and adrenal gland of male albino rats after 2, 4, 8 and 24 hrs of injection. Administration of either indomethacin or meloxicam was found to have a variety of actions in monoamine levels, producing either potentiation, no effect, or inhibition. The most pronounced increasing effects were observed with indomethacin on DA levels after 2, 4 and 8 hrs, on NE levels after 4 and 8 hrs and on 5-HT levels after 2 and 4 hr in most of the tissues examined. The increase was also observed in DA levels after 4 and 24 hrs following meloxicam treatment. However, the most prominent inhibitory effect was noticed following treatment with meloxicam in NE levels after 2 and 8 hrs and in 5-HIAA levels after the different time intervals in all the selected tissues. It is possible to conclude that the potentiating effect of indomethacin and meloxicam may be due to inhibition of cyclooxygenase pathway for the oxidative metabolism of arachidonic acid, with consequent conversion of the acid into lipooxygenase system and the generation of products which enhance amine release. Meanwhile the inhibitory effect of two drugs may be related to inhibition of protein kinase C blockade of oxidative phosphorylation and a reduction in the ATP content of the tell required for amine release