INTRACELLULAR CALCIUM SIGNALS ARE ENHANCED FOR DAYS AFTER PAVLOVIAN CONDITIONING

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.