In vitro analysis of the feeding neural circuit in Aplysia after long‐term sensitization training

Abstract

The effects of long‐term sensitization (LTS) training on defensive responses in Aplysia are well understood behaviorally and cellularly. Conversely, LTS training's effects on feeding are only marginally understood. 24 h after LTS training, the tail‐siphon withdrawal reflex is enhanced and, concomitantly, feeding is suppressed. The goal of this study was to characterize LTS training's effects on the feeding central pattern generator (CPG). During biting, the nerves controlling radula protraction, closure, and retraction express patterns of buccal motor activity (BMPs) generated by the CPG. LTS training's effects on BMP production were examined by recording extracellularly from the I2 (protraction), Rn.1 (closure), and Bn.2,1 (retraction) nerves while activating the CPG via electrical stimulation of the Bn.2,3 nerve. Classification of BMPs as ingestive or egestive has been previously established both in vivo and in vitro. Results indicated no change in total CPG output between trained and untrained animals. However, differences in the types of BMPs generated emerged. Trained animals showed a suppression of ingestive BMPs and a reduced ability of the CPG to generate complete BMPs. These changes in BMP production represent correlates for LTS training‐induced suppression of feeding at the circuit level, and might explain for the changes in biting behavior measured in vivo. Funded by NSF IOS – 1120304.