Cerebral and buccal neurons involved in buccal motor pattern generation in Achatina fulica

In the African giant snail, Achatina fulica, two pairs of cerebral neurons, v-CDNs and Cls, and ten pairs of buccal neurons, Bls-B10s, were identified. B1-B6 and B10 were the excitatory motoneurons of buccal muscles. B7 and B8 innervated salivary ducts and B9 extended its axons to the cerebral ganglia although their functions were not clear yet. Serotonergic v-CDN exerted excitatory effects on various neurons in the buccal ganglia and had modulatory effects on buccal muscles. When v-CDN, Cl or B1 was continuously fired, each one could initiate and maintain the rhythmic motor activity (RMA) in the buccal ganglia of reduced preparation. Taste stimulation of the lip often elicited RMA. Nevertheless, v-CDN and B1 were not always excited by taste stimuli, and they appeared not to be critical elements in the generation of feeding rhythm. In contrast, Cl responded to taste stimuli with burst of spikes. Thus, C1 may play a role in taste-induced rhythm generation in intact animal.