Effect of S-adenosyl-L-methionine on impairment of working memory induced in rats by cerebral ischemia and scopolamine.

A repeated acquisition procedure in a 3-panel runway apparatus was used to investigate the effects to S-adenosyl-L-methionine (SAM) on impairment of working memory produced either by cerebral ischemia or by scopolamine in rats. Cerebral ischemia (2-10 min) produced duration-dependent increases in the number of errors (pushes made on the two incorrect panels located at each choice point) and increased latency (time before the rat reached the goal box). The increase in errors induced by a 5 or 10 min period of ischemia decreased gradually in subsequent training sessions, returning to the control levels in 6 days. The increases in both errors and latency induced by 5 min of ischemia were significantly reduced by 100 and 180 mg/kg SAM administered i.p. immediately after blood recirculation and 1 h before a test conducted 24 h after ischemia. SAM at doses up to 180 mg/kg nevertheless failed to reduce the increases in errors and latency if they were induced by 0.56 mg/kg of scopolamine. These results suggest that SAM has a beneficial effect on memory that has been impaired by cerebral ischemia.