Pre-training adrenaline recovers the amnestic effect of Met-enkephalin in demedullated rats

The intracerebroventricular administration of 25 ng of Met-enkephalin causes retrograde amnesia for a shuttle avoidance task in intact rats. In demedullated rats, this effect of Met-enkephalin was lost. Intraperitoneal injection of 1.2 micrograms/kg adrenaline recovered the amnestic effect of Met-enkephalin. These results confirm the idea that the amnestic effect of Met-enkephalin is centrally mediated and that adrenal enkephalins do not seem to be important to the amnestic effect of Met-enkephalin since adrenaline recovers this effect in demedullated rats.