Identification of a GABA-containing cerebral-buccal interneuron-11 in Aplysia californica.

The cerebral-buccal interneurons (CBIs) in Aplysia are a group of inter-ganglionic projection neurons that regulate feeding motor programs. In this study, electrophysiological and immunocytological methods were used to identify a previously uncharacterized CBI, designated CBI-11. CBI-11 is a gamma-aminobutyric acid (GABA)-immunoreactive neuron located in the G cluster of the cerebral ganglion. Firing CBI-11 produced fast picrotoxin-sensitive inhibitory postsynaptic potentials (IPSPs) in buccal motor neuron B3. Local application of GABA to B3 produced a picrotoxin-sensitive hyperpolarization that reversed at the same membrane potential as the IPSPs elicited by stimulation of CBI-11. Together, these observations indicate that CBI-11 utilizes GABA as its transmitter. Finally, stimulation of CBI-11 elicited rhythmic motor programs in quiescent buccal ganglia. Thus, CBI-11 is a GABAergic CBI that can function as a motor program initiator.