Post-test apamin injection suppresses a Kamin-like effect following a learning session in mice

BALB/c mice were trained in a partial acquisition session of an appetitive bar-pressing task. They then received an immediate post-acquisition i.p. injection of either saline or apamin 0.2 mg kg-1. Each group was submitted to a retention test that was delayed either 25, 85 or 180 min after initial acquisition. In saline-injected groups retention of the original training was a U-shaped function of intersession interval with a significant drop in performance (Kamin-like effect) at the 85 min time interval. In contrast, at this same time, apamin injected subjects made significantly more reinforced responses than control animals. The suppression of the Kamin-like effect by apamin could be a consequence of an acceleration of the neuronal mechanisms implicated in consolidation and long-term memory storage processes.