Glyphosate and glyphosate‐based herbicide exposure during the peripartum period affects maternal brain plasticity, maternal behaviour and microbiome

Abstract

Glyphosate is found in a large array of non‐selective herbicides such as Roundup® (Monsanto, Creve Coeur, MO, USA) and is by far the most widely used herbicide. Recent work in rodent models suggests that glyphosate‐based herbicides during development can affect neuronal communication and result in altered behaviours, albeit through undefined mechanisms of action. To our knowledge, no study has investigated the effects glyphosate or its formulation in herbicide on maternal behaviour and physiology. In the present study, relatively low doses of glyphosate (5 mg kg‐1 d‐1), Roundup® (5 mg kg‐1 d‐1 glyphosate equivalent), or vehicle were administered by ingestion to Sprague‐Dawley rats from gestational day (GD) 10 to postpartum day (PD)22. The treatments significantly altered licking behaviour toward pups between PD2 and PD6. We also show in the dams at PD22 that Roundup exposure affected the maturation of doublecortin‐immunoreactive new neurones in the dorsal dentate gyrus of the hippocampus of the mother. In addition, the expression of synaptophysin was up‐regulated by glyphosate in the dorsal and ventral dentate gyrus and CA3 regions of the hippocampus, and down‐regulated in the cingulate gyrus. Although a direct effect of glyphosate alone or its formulation on the central nervous system is currently not clear, we show that gut microbiota is significantly altered by the exposure to the pesticides, with significant alteration of the phyla Bacteroidetes and Firmicutes. This is the first study to provide evidence that glyphosate alone or in formulation (Roundup) differentially affects maternal behaviour and modulates neuroplasticity and gut microbiota in the mother.

Canadian Arctic Contaminants and Their Effects on the Maternal Brain and Behaviour: A Scoping Review of the Animal Literature

“…Similar findings were shown in a cross-foster design study whereby combined data from PCB-exposed rat dams (2 mg/kg bw/day) rearing PCB-exposed pups and non-exposed dams rearing PCB-exposed pups displayed increases in time grooming as well as in licking and nursing bouts [76]. Recent literature using a glysophate-based herbicide (Roundup) presents similar increases in maternal licking behaviour [102]. Conversely, maternal bisphenol A exposure has shown significant reductions in licking and grooming behaviour [103].…”

The parental brain and behavior: A target for endocrine disruption

“…Numerous compounds are known to affect mammary gland development (for example Ventura et al, 2016;Perrot-Applanat et al, 2018;Mandrup et al, 2015;LaPlante et al, 2018) but the outcome on maternal behavior was, to our knowledge not investigated. In the same line of idea, some EDC seem to act on the maternal brain and behavior partly by modulating the dam's microbiota, as suggested for BPA (Javurek et al, 2016) and for glyphosate (Dechartres et al, 2019). This point to the importance of looking at maternal behavior, like any other behavior, as an output from a whole organism/individual and not only as a consequence of a few changes in neuronal activation.…”

“…The anti-androgenic chemical chlorpyrifos, an organophosphate insecticide, increased pup grooming in female mice exposed during pregnancy (Venerosi et al, 2009). Finally, other known reproductive toxicants including the herbicides sulentrazone (rat: de Castro et al, 2007) and glyphosate (Dechartres et al 2019), the insecticides carbaryl (meadow jumping mouse: Punzo, 2003) and fipronil (rat: Udo et al, 2014), and the herbicide 2,4-dichlorophenoxyacetic acid (rat: Sturtz et al, 2008) altered numerous aspects of maternal behavior including retrieval behaviors,…”

Toxicomicrobiomics: The Human Microbiome vs. Pharmaceutical, Dietary, and Environmental Xenobiotics

“…Consequently, it affects brain plasticity, maternal behavior, and parenting (Dechartres et al, 2019).…”