Synaptic connections in the buccal ganglia of Aplysia mediated by an identified neuron containing a CCK/gastrin-like peptide co-localized with acetylcholine.

The identified neuron, B13, located bilaterally in the buccal ganglion of the marine mollusc Aplysia californica, contains a classical neurotransmitter (acetylcholine) and a cholecystokinin/gastrin-like (CCK/G-li) peptide. The following study demonstrates that B13 makes direct synaptic connections with several identifiable postsynaptic follower neurons. These follower neurons also receive convergent input from previously identified cholinergic neurons, B4 and B5, which do not contain a CCK/G-li peptide. The cholinergic responses mediated by B4/B5 and B13 are similar, including in at least one buccal follower, a two-component inhibitory response not seen in previous studies of the buccal ganglia circuits. However, when the cholinergic responses are blocked by appropriate antagonists, a residual, slow depolarizing, chemically-mediated response is observed in two of the identifiable followers when action potentials are evoked in B13 but not when action potentials are evoked in B4 or B5.