Research reportProtein synthesis is not required for acquisition, consolidation, and extinction of high foot-shock active avoidance training

- Cycloheximide did not hinder acquisition of low- and high-intensity active avoidance training.
- Cycloheximide impairs consolidation and extinction of low-intensity training.
- High-intensity training protects consolidation from cycloheximide impairing effects.
- High-intensity training protects extinction from cycloheximide impairing effects hinder.

Long-term memory of active avoidance in mice is not disturbed by administration of protein synthesis inhibitors (PSIs) when relatively high levels of training are used, whereas a detrimental effect is produced with lower levels of training. PSIs also disrupt extinction of avoidance behaviors in rodents, but it is not clear whether PSIs also affect this form of learning when the behavior to be extinguished was produced by a high level of training. Experiment 1 demonstrated that rats treated with the PSI cycloheximide (CXM) 30 min before training developed normal acquisition after training with either high or low foot-shock stimulation, but that memory consolidation was hindered only after low foot-shock training. Experiment 2 demonstrated that CXM disrupted extinction when administered before the first of a series of extinction sessions when low foot-shock intensity was used during training; in contrast, after training with a higher foot-shock, the PSI treatment only interfered transiently with extinction. These results indicate that acquisition, consolidation, and extinction of active avoidance learning produced by high aversive stimulation are not dependent on protein synthesis and that these processes are governed by mechanisms different from those underlying moderate forms of learning.