The effect of aluminum on conditioned avoidance response (CAR) in mice

Aluminum is used in medical products and some parenteral products (Vaccines) contain aluminum. In a study of neurotoxicity of aluminum in mice, four groups of CD1 mice (5 males and 5 females per dose level) were treated as follows: group one drank 1.0% of aluminum (as AlCl3) during the weaning period from day 1 to 8 weeks of age; group two drank AlCl3 from 1 month to 4 months of age; group three mice (1 month old) were injected i.p. with 10, 30 and 100 mg of aluminum/kg/day for two days; group four mice (1 month old) were injected s.c. with 3, 10, and 30 mg of aluminum/kg/day for 2 days. Controls received the vehicle only. All mice were trained for CAR five times at 2 months of age. The CAR of mice that ingested AlCl3 during the weaning period to 8 weeks of age was lowered by 26% compared to the control group, which achieved 46% of CAR after five training sessions. Also, the retention of CAR was reduced to 30% whereas that of the control group remained at the same level after 1 month. CAR values of group two did not differ from those of its control. CAR of group three (at 30 mg/kg i.p.) was 36% lower than controls. CAR of s.c. group four (3, 10, and 30 mg/kg) was lowered to 16%-28% of the control; CAR retention was reduced to 18%. Therefore, the oral ingestion of aluminum induced neurotoxicity in mice which may be seen only at an early age, but injection of aluminum can cause neurotoxicity at any age.