Chlorpyrifos and neuroendocrine function: Concerns for research with free-living mammal populations

Chlorpyrifos is an organophosphate pesticide widely used in many countries to control insect pests. This pesticide causes neurotoxic effects in target species through cholinergic toxicity, but also has several secondary effects on neural substrates. Chlorpyrifos can modulate several neurotransmitters, including the nonapeptides oxytocin and vasopressin which are well-known for their modulation of social behavior and reproduction. Scientists have championed the need for the use of non-traditional models to understand the underpinnings of these nonapeptides in the evolution of social behavior. However, exposure to pesticides like chlorpyrifos can alter the organization of vasopressin and oxytocin circuits during neurodevelopment, which then leads to changes in adult behavior. In this review, we explore the research that connects chlorpyrifos and the nonapeptides, emphasizing the potential impacts of this pesticide on behavioral neuroendocrinology using these non-traditional models.