Manganese-induced damage to the serotoninergic system is associated with the development of anxiety and depression

Manganese-induced damage to the serotonergic system was considered to be one of the causes of the development of affective disorders, such as depression and anxiety. However, in the literature, only a few studies could be found on the mechanisms that described the influence of excess manganese levels on the serotonergic system of the central nervous system (CNS). Therefore, it was an important medical and biological task to study the mechanisms underlying the development of affective disorders. This work focused on studying the main mechanisms of the development of affective disorders in male rats under conditions of chronic intranasal administration of manganese chloride (MnCl₂) at a dose of 5 mg/kg for 34 consecutive days. We showed that chronic intranasal administration of MnCl₂ led to the development of increased anxiety and depression in rats, the cause of which was a decrease in serotonin concentration in the striatum and an increase in serotonin concentration in the hippocampus, caused by changes in the expression of tryptophan hydroxylase (tph-2) and aromatic L-amino acid decarboxylase (aadc) mRNA.