IDENTIFICATION OF SPECIFIC MESSENGER-RNAS AFFECTED BY TREATMENTS PRODUCING LONG-TERM FACILITATION IN APLYSIA

Neural correlates of long-term sensitization of defensive withdrawal r eflexes in Aplysia occur in sensory neurons in the pleural ganglia and can be mimicked by exposure of these neurons to serotonin (5-HT). Stu dies using inhibitors indicate that transcription is necessary for pro duction of long-term facilitation by 5-MT. Several mRNAs that change i n response to 5-HT have been identified, but the molecular events resp onsible for long-term facilitation have not yet been fully described. To detect additional changes in mRNAs, we investigated the effects of 5-HT (1.5 hr) on levels of mRNA in pleural-pedal ganglia using in vitr o translation. Four mRNAs were affected by 5-MT, three of which were i dentified as calmodulin (CaM), phosphoglycerate kinase (PGK), and a no vel gene product (protein 3). Using RNase protection assays, we found that 5-HT increased all three mRNAs in the pleural sensory neurons. Ca M and protein 3 mRNAs were also increased in the sensory neurons by se nsitization training. Furthermore, stimulation of peripheral nerves of pleural-pedal ganglia, an in vitro analog of sensitization training, increased the incorporation of labeled amino acids into CaM, PGK, and protein 3. These results indicate that increases in CaM, PGK, and prot ein 3 are part of the early response of sensory neurons to stimuli tha t produce long-term facilitation, and that CaM and protein 3 could hav e a role in the generation of long-term sensitization.