Previous observations have implicated GABA as a neurotransmitter relea
sed by the vestibular sensory neurons (''hair cells'') of the snail He
rmissenda onto visual sensory neurons, the type B cells, whose cell bo
dies are the sites of biophysical and biochemical changes during and f
ollowing Pavlovian conditioning. Still other observations demonstrated
that light-GABA pairings that simulate stimuli presented during Pavlo
vian conditioning cause prolonged elevation of intracellular Ca2+ and
transformation of GABA-induced synaptic inhibition into excitation. In
tracellular Ca2+ signals in response to GABA perfused onto the postsyn
aptic type B terminal branches are shown here to be prolonged on days
after conditioning, but not after control paradigms. These and past re
sults demonstrate two separate sites, i.e., the cell body and the term
inal branches, for learning-induced changes after Pavlovian conditioni
ng.