Inhibition of protein synthesis blocks long-term enhancement of generator potentials produced by one-trial in vivo conditioning in Hermissenda.

A one-trial in vivo conditioning procedure produces short- and long-term cellular changes that can be detected in identified sensory neurons of the pathway mediating the conditioned stimulus. The memory of the associative experience in the conditioned stimulus pathway is expressed by short- and long-term enhancement of light-evoked generator potentials recorded from identified lateral and medial type B photoreceptors within the eyes of Hermissenda. To identify mechanisms of the induction and expression of short- and long-term enhancement in identified photoreceptors, we have investigated the effects of inhibiting protein synthesis during the application of the one-trial in vivo conditioning procedure. Anisomycin (1 microM) present during and after the conditioning trial blocked long-term enhancement without affecting the induction or expression of short-term enhancement. Application of a control compound, deacetylanisomycin (1 microM), or delaying the application of anisomycin until 1 hr after the conditioning trial did not block either long- or short-term enhancement. These results indicate that synthesis of proteins during or shortly after training may be a critical step in the formation of long-term memory of the associative experience.