The contribution of stressor intensity, duration, and context to the stress-induced facilitation of associative learning.

Exposure to an acute stressor of restraint and intermittent tailshock facilitates acquisition of the classically conditioned eye-blink response 24 h after stressor cessation. The contribution of stressor intensity, duration, and context was determined. Male rats exposed to 90 or 30 1-mA tailshocks exhibited sensitization to an auditory cue of 86 dB and facilitated acquisition of the conditioned response, whereas rats exposed to 90 0.5-mA tailshocks or restraint alone only exhibited sensitization. Rats exposed to the 5 1.0-mA tailshocks (and 5 min of restraint) exhibited neither sensitization nor facilitated acquisition. Rats stressed in the same context 48 and 96 h earlier exhibited sensitization and facilitated acquisition relative to those stressed in a different context. Neither stressed group exposed to unpaired stimuli responded to the CS, and thus there was no pseudodconditioning. Together, these results dissociate the stress-induced sensitization from the facilitated learning. They also indicate that the facilitated learning is particularly sensitive to stressor intensity and contextual cues.