Aluminium-induced changes in the rat brain serotonin system

Aluminium exposure, apart from producing cholinotoxicity, can include changes in other neurotransmitter levels since neurotransmitter levels are closely interrelated. Reports of aluminium (Al) effects on brain neurotransmitters are limited. To investigate the effect of Al on the rat brain serotonergic system, the present study was conducted to explore brain region-specific changes and duration-specific changes. Male Wistar albino rats were exposed orally to Al chloride (AlCl3.6H2O; 320 mg/kg body weight) daily for up to 60 days and changes in the 5-hydroxytrytamine (5-HT) and its metabolite 5-hydroxyindole acetic acid (5-HIAA) levels were observed after 4, 14 and 60 days of exposure in olfactory lobe (OLB), cerebellum (CBL), pons (PON), medulla oblongata (MOB), spinal cord (SPI), hypothalamus (HYP), hippocampus (HIP), striatum (STR), midbrain (MBR) and cortex (COR) brain regions. Significantly increased 5-HT levels observed in brain regions OLB (60 days), HIP (4,14 days), STR (14 days), HYP (14, 60 days), MBR (4 and 14 days), PON (4 days), MOB (4 days) and SPI (4, 14 and 60 days) following Al exposure may be due to Al deactivating 5-HT system by decreased release and subsequent breakdown of 5-HT. Decreased 5-HT levels observed in cerebral COR, HIP (60 days) and in CBL after 4 and 60 days of exposure suggest an inhibitory effect of Al on the 5-HT system due to withdrawal of cholinergic input in these brain regions. 5-HIAA level changes correlate with 5-HT level changes in many brain regions studied. The results reveal that the neurochemical changes due to Al were dependent on the duration of exposure and are brain-region-specific. The observed changes may be related to the cholinergic toxicity of Al.