High doses of aspartame have no effects on sensorimotor function or learning and memory in rats.

Acute or repeated (14 days) intragastric administration of L-d-aspartyl-L-phenylalanine methyl ester (aspartame) suspended in saline and Tween-80 in doses of up to 1,000 mg/kg had no significant effect in male Fischer-344 rats on routine measures of sensorimotor function, including spontaneous motor activity, acoustic startle reflex and prepulse inhibition. Other experiments found that aspartame (500 or 1,000 mg/kg) had no significant effect on acquisition of passive or active avoidance or a spatial, reference memory task in the Morris water maze. A series of separate studies found that aspartame had no effects in rats fasted 24 hours prior to testing, or if it was suspended in carboxymethylcellulose or administered by the intraperitoneal route. Under the conditions of these experiments, large doses of aspartame have no significant neurobiological effects in adult rats as measured by procedures known to be sensitive to the neurobiological effects of neurotoxicants, including convulsants, organochlorine insecticides and heavy metals.