Cholinesterase activity of ganglia of gastropoda, Lymnaea stagnalis and Planorbarius corneus—I. Effect of anti- cholinesterase agents on giant neurone depolarization by acetylcholine and its analogues

Abstract

1. 1. The action of eserine and two organophosphorous cholinesterase inhibitors on the sensitivity of identified neurones of Lymnaea stagnalis and Planorbarius corneus to cholinergic agonists was studied with microelectrodes. 2. 2. Eserine did not affect the action of ACh on Lymnaea neurones but did enhance the depolarizing potency of BuChE substrates, BuCh and D-6, as much as 1·6-fold and 13-fold respectively. 3. 3. On Lymnaea neurones the BuChE selective inhibitor, compound GT-165, potentiated D-6, BuCh, ACh and AChE substrate, acetyl-β-methylcholine (mecholyl), as much as 33·8-, 3·7-, 4- and 3·2-fold respectively. The selective inhibitor of AChE, compound Gd-42, increased the action of ACh 6·9 times and that of mecholyl four times, but did not change the D-6 and BuCh depolarization. 4. 4. From these findings a conclusion may be drawn about high cholinesterase activity in Lymnaea ganglia; there seems to exist at least two different enzymes. This was emphasized by the data of experiments with a consecutive application of Gd-42 and GT-165. 5. 5. With the inhibitors used we failed to reveal any essential cholinesterase activity in Planorbarius ganglia.