Effect of combinations of insulin, glucose and scopolamine on radial arm maze performance

Previous research has shown that glucose is an effective agent in facilitating memory performance and in attenuating scopolamine-induced amnesia. Although insulin has not been shown to facilitate unimpaired memory, a previous study has demonstrated that insulin can also attenuate scopolamine-degraded memory. The present study was designed to determine how different combinations of insulin, glucose and scopolamine affect memory. It involved nine rats whose memory was assessed through performance in a win-shift radial arm maze task under different drug treatments. A 2 x 2 x 2 (insulin x glucose x scopolamine) within-subjects design with a 5-h drug test interval was employed. Scopolamine disrupted memory performance, and both glucose and insulin-counteracted this disruption. Combining the glucose and insulin treatments did not increase their ability to attenuate scopolamine deficits but slightly decreased this effect. Glucose tended to enhance memory, even in the absence of scopolamine, whereas insulin had no effect on memory in the absence of scopolamine. Blood glucose levels were measured and did not indicate changes caused by drug treatments. The memory effects may have been due to the acetylcholine-agonist actions of glucose and insulin, an interpretation consistent with previous research findings. (C) 1997 Elsevier Science Inc.