9,10-Dihydroergotalkaloids as inhibitors of acetylcholinesterase.

A kinetic analysis of the interaction of 9,10-dihydroergotalkaloids with electrophorus electricus acetylcholinesterase [E.3.1.1.7] and acetylthiocholine as substrate shows a mixed type of inhibition of this enzyme. The inhibitor constants Ki were found to be for 9,10-dihydroergokryptine 198 mumol, 9,10-dihydroergotamine 144 mumol, 9,10-dihydroergocristine 117 mumol. A more potent inhibitor is ergotamine with the inhibitor constant Ki = 15 mumol and a mixed type of inhibition.