Monoamine oxidase (MAO) is inhibited by imidazoline binding site I2 specific ligands in vitro

W. Raasch*, H. Muhle, P. Dominiak

*Corresponding author for this work
6 Citations (Scopus)


Two types of imidazoline binding sites (I1- and I2-BS) were identified until now and less is known about their function, especially about I2-BS. The hypothesis of the present study was that I2-BS ligands affect monoamine oxidase (MAO) activity because I2-BS was found to be located on mitochondria. Therefore, different imidazoline-, imidazole- and guanidinederivatives and α-adrenoceptor ligands were taken with regard to their ability to affect MAO activity in vitro. Enzyme kinetic was established in the presence of inhibitors (10-6-10-2 M). We found that MAO activity was decreased relatively to maximum effects (without inhibitors) significantly at concentration of 100 μM/l by substances with high affinity to I2-BS (antazoline: -76.5, idazoxan: -70.1, cirazoline: -64.1) than by I1-ligands (efaroxan: -15.1, rilmenidine: -31.2, clonidine: -12.0, moxonidine: -8.2). Substances with highest inhibitory effect were BDF 8082 (-93.2) and 2-(2-benzofuranyl)-2 -imidazoline (-90.9). Agmatine, the endogenous ligand at IBS, also decreased MAO activity (-35.6) whereas its precursor L-arginine had no effect. The mechanism of inhibition is non-competitive because v(max) but not k(m) was affected. From our data we conclude that the reduction in MAO activity following blockade of I2- BS confirms our hypothesis of an I2 regulatory binding site at MAO and therefore its functional importance.

Original languageEnglish
JournalPharmaceutical and Pharmacological Letters
Issue number1
Pages (from-to)42-45
Number of pages4
Publication statusPublished - 1996

Research Areas and Centers

  • Academic Focus: Center for Infection and Inflammation Research (ZIEL)


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