Environmental exposure to common pesticide induces synaptic deficit and social memory impairment driven by neurodevelopmental vulnerability of hippocampal parvalbumin interneurons

Environmental exposure to pesticides at levels deemed safe by regulatory agencies has been linked to increased risk for neurodevelopmental disorders. Yet, the mechanisms linking exposure to these disorders remain unclear. Here, we show that maternal exposure to the pesticide deltamethrin (DM) at the no observed adverse effect level (NOAEL) disrupts long-term potentiation (LTP) in the hippocampus of adult male offspring three months after exposure, a phenotype absent in female offspring. Clonazepam, a GABAa receptor agonist, rescued this deficit, indicating impaired hippocampal GABAergic signaling. Recordings from CA1 pyramidal neurons, complemented by MALDI mass spectrometry imaging, showed an imbalance in excitatory/inhibitory tone. Using a combination of parvalbumin (PV)-Cre transgenic mice and hippocampal injection of designer receptors exclusively activated by designer drugs (DREADDs), we show that developmental DM exposure reduces hippocampal PV interneuron intrinsic firing. DREADD activation rescued both PV interneuron firing and LTP deficits. Complementary behavioral experiments revealed a deficit in social memory, a behavior relevant to autism spectrum disorder (ASD) symptomatology, which was restored by DREADD activation. Overall, these results establish a novel mechanistic link between maternal exposure to DM at the NOAEL and known cellular, circuital, and behavioral vulnerabilities, indicating it is a potential driver in the exposome of ASD.