Electrophysiological responses to metaldehyde in neurones of the feeding circuitry of the snail Lymnaea stagnalis

The molluscicide, metaldehyde, induced bursting activity and paroxysmal depolarizing shifts in identified motoneurons in the feeding system of Lymnaea stagnalis . This was accompanied by a reduction in after-spike hyperpolarization and action potential broadening. The cerebral giant cells, a pair of interneurons in the feeding circuitry, also showed increased firing activity and marked spike broadening in response to metaldehyde; action potential duration increased from 10 to 20 msec to up to 800 msec. Rhythmic feeding motor output, generated in the isolated central nervous system, was disrupted following application of metaldehyde; activity in central pattern-generating interneurons and in motoneurons appeared to become uncoupled. The effects of metaldehyde on neurons in the feeding system may partly explain the suppression of feeding behavior seen in whole animals fed on metaldehyde baits.