Effect of Combined Fluorine and Aluminum Exposure during Pregnancy and Lactation on Spatial Learning and Memory Ability and Amino Acid Neurotransmitters in Filial Rats

Objective To investigate the effect of combined fluorine (NaF) and aluminum (AlCl₃) exposure during pregnancy and lactation on the spatial learning and memory ability and amino acid neurotransmitters in filial rats.

Methods Fifty-four adult rats were assigned by random to 9 groups, six rats in each group, the female-male ratio was 2:1, twelve filial rats were selected randomly in each group. The exposure of fluorine and aluminum in maternal rats was conducted by drinking water freely from the 0^th day after conception to the 22^nd day after giving birth and weaning; the filial rats were treated by drinking water after weaning to the 60^th day of age. The concentration of NaF and AlCl₃ in drinking water for each group was (0, 0), (100, 0), (200, 0), (0, 500), (0, 1000), (100, 500), (100, 1000), (200, 500) and (200, 1000) mg/L. The learning and memory ability of filial rats was tested in Morris water maze, and the excretion of urine in 12 hours was collected. After killed, filial rats' brains were kept. The content of fluorine in urine and brain of filial rats was tested by ion selected electrode method; the content of aluminium in urine and brain was tested by inductively coupled plasma atomic emission spectrometry; the pathomorphological changes in hippocampus stained by HE were observed under microscope; the level of GABA and Asp in hippocampus was assayed by enzyme-linked immunosorbent assay; the level of Glu and Gly in hippocampus was assayed by automatic amino acid analyzer.

Results Compared with the control group, the content of fluorine in urine of fluorine alone or combined fluorine and aluminium exposure group was higher (P < 0.05); the content of aluminium in urine of aluminium alone and combined fluorine and aluminium exposure group was higher (P < 0.05). The escape latency was prolonged and the number of times across platform was reduced in all exposure groups (P < 0.05). The level of Glu and Asp in the hippocampus of filial rats in all exposure groups was less (P < 0.05), except in the low fluorine + low aluminium group and the low fluorine + high aluminium group. The level of GABA in hippocampus of exposure groups was higher (P < 0.05); the level of Gly in hippocampus of all groups was not significantly different. The higher exposure of aluminium in drinking water, the more fluorine in urine. The pathological injury in CA3 area of hippocampus was aggravated with the increase of fluorine and aluminium exposure. It was mainly a synergistic interaction of combined fluorine and aluminium exposure on urinary fluorine, but it was only a slight antagonistic interactions of combined fluorine and aluminum exposure on escape latency and the number of times across platform, fluorine and aluminium content in pallium, and Glu and GABA level in hippocampus (P < 0.05).

Conclusions Under the experimental condition, the effect of combined fluorine and aluminium exposure on the content of fluorine and aluminium in urine was a synergistic interaction; the effect of combined fluorine and aluminium exposure on the escape latency and the number of times across platform, the content of fluorine and aluminium in pallium, and the level of Glu and GABA in hippocampus was mainly a slight antagonistic interaction. The decrease of Glu and Asp and the increase of GABA in hippocampus might patricipater in the mechanisms for combined fluorine and aluminum exposure on the damage of spatial learning and memory ability in filial rats.