Meeting Abstract

P1.128  Tuesday, Jan. 4  Neuronal mechanisms of aversive taste conditioning in Lymnaea stagnalis SUNADA, Hiroshi*; HORIKOSHI, Tetsuro; SAKAKIBARA, Manabu; Graduate school of biosci., Tokai univ; Graduate school of biosci., Tokai univ; Graduate school of biosci., Tokai univ sunada@nerve.fb.u-tokai.ac.jp

Conditioned taste aversion (CTA) was carried out on the pond snail, Lymnaea stagnalis. The conditioned stimulus (CS) was sucrose which elicits feeding behavior, while the unconditional stimulus was a tactile stimulus to the head which causes feeding to be suppressed. The neuronal circuit that drives feeding behavior in Lymnaea is well work out. We therefore compared the electrophysiological responses elicited by the CS in conditioned vs. naive snails in 3 classes of neurons involved with feeding behavior. The cerebral giant cell (CGC) modulates feeding behavior, N1 medial neuron (N1M) is one of the central pattern generator neuron that organizes feeding behavior, whilst B3 is a motor neuron active during the rasp phase of feeding. We found no change in the resting membrane potential and spontaneous generating impulse frequency of the CGC between trained vs. naive snails. There was, however, a significant increase in spontaneous activity; a disappearance of bursting activity typically initiated by the CS. These neuronal modifications are consistent with the behavioral phenotype elicited by the CS following conditioning. In the CTA it has not yet established neuronal architecture that elicits fictive feeding and that controls withdrawal behavior, we examined the neuronal connection between CGC and right pedal dorsal11 neuron (RPeD11) with electrophysiological techniques. RPeD11, which controls the withdrawal behavior, had monosynaptic inhibitory-chemical synapse with CGC. This synaptic connection was thought to be crucial for the CTA, we next examined whether the CGC, N1M and B3 behaved in the same way as observed in-vivo conditioning using semi-intact preparation.