Chronic exposure to metam sodium-based pesticide in mice during adulthood elevated anxiety and depression-like behaviors: Involvement of serotoninergic depletion and gut microbiota dysbiosis.

Metam sodium-based pesticide (MS-BP) is widely used in agriculture and public health. We have previously demonstrated that maternal exposure to MS-BP resulted in sensorimotor alterations in mice offspring with long-lasting deficits including anxiety- and depression-like behaviors. Here, we project to verify whether these two neurobehavioral effects occur during adulthood following direct exposure to MS-BP and whether it results in changes in the serotoninergic system and gut microbiota. Our findings showed that chronic exposure to MS-BP increased anxiety- and depression-like behaviors, accompanied by a depletion of serotonin-like neurons within the dorsal raphe nucleus and a reduction in serotoninergic terminals in the infralimbic cortex and the basolateral amygdala. In addition, all MS-BP-exposed animals exhibited a reduced total bacterial number and diversity of gut microbiota. Taken together, our data demonstrated that MS-BP-induced behavioral changes could be related to the impairment of the serotoninergic system and gut microbiota dysbiosis.