The identification of acetyl-l-carnitylcholine in rat brain extracts and the comparison of its cholinomimetic properties with acetylcholine

Acetyl-l-carnitylcholine (l-ACCh) was identified in rat brain extracts on paper chromatograms developed in butanol–water for 138 h. l-ACCh was also identified in brain extracts fractionated on t.l.c. plates and on Sephadex G-10 columns. In every instance l-ACCh was separated from the acetylcholine (ACh) present and the ACh-like activity of l-ACCh was about 20% of the total activity in the extract. Both l-ACCh and ACh were found to be inseparable in a variety of chromatographic systems including electrophoresis. Treatment of these choline esters with cholinesterases showed that while true acetylcholinesterase hydrolyzed both l-ACCh and ACh, pseudocholinesterase destroyed only ACh. On a molar basis, the ACh-like activity of ACCh is one-half that of ACh on both the guinea pig ileum and frog rectus preparations. Like ACh, the ratio of the nicotinic to muscarinic potency of l-ACCh is unity. Mixtures of l-ACCh and ACh show summation of ACh-like activity on both the guinea pig ileum and frog rectus preparations.