Theses and Dissertations

Issuing Body

Mississippi State University


Carr, Russell

Committee Member

Ross, Matthew K.

Committee Member

Eells, Jeffrey B.

Committee Member

Nanduri, Bindu

Committee Member

Edelmann, Mariola J.

Date of Degree


Document Type

Dissertation - Open Access


Environmental Toxicology

Degree Name

Doctor of Philosophy


College of Veterinary Medicine


Department of Comparative Biomedical Sciences


Chlorpyrifos (CPF) is one of the most widely used organophosphorus insecticides (OPs). The developmental exposure to low levels of CPF results in the inhibition of the endocannabinoid metabolizing enzyme fatty acid amide hydrolase (FAAH) and in altered emotional behavior (increased social play) without affecting the acetylcholinesterase, the canonical target of OPs. However, the molecular mechanisms responsible for this increased social play are not known. In this study, male rat pups were exposed orally to either corn oil, 0.75 mg/kg CPF, or 0.02 mg/kg PF-04457845 (PF; a specific inhibitor of FAAH) daily from postnatal day 10 (PND10) - PND16. This dosage of CPF does not alter brain cholinergic activity but inhibits FAAH. Once these rats reached adolescence (PND38), they were divided into two cohorts and each cohort contained all treatments. One cohort underwent social behavior testing and the other cohort remained naïve to behavioral testing. Following testing, the amygdala was collected from each cohort and protein expression was determined using a labelree shotgun proteomic approach. The obtained differentially expressed proteins from the different cohorts were analyzed by DAVID and Ingenuity Pathway Analysis software. Comparison of control non-behavior and control behavior rats suggests that social play altered the systems involved in the regulation of reward such as the opioid, dopaminergic, and serotonergic systems. These data also suggest that synaptic levels of GABA and glutamate increased during play. Comparison of non-behavior control and treated rats suggests that FAAH inhibition resulting from developmental exposure to CPF and PF persistently affects glutamatergic and GABAergic signaling. These data also suggest that there is a similar pattern of protein expression between CPF and PF. Comparison of the data from the behavioral groups of rats suggests that alterations in glutamatergic and GABAergic signaling and improper activation of opioid signaling could be responsible for the increased social play behavior. These alterations in the neurotransmitter signaling were observed in both CPF and PF treated rats. Overall, the results suggest that FAAH inhibition by either CPF or PF leads to alterations in opioid, glutamatergic, and GABAergic signaling that could be responsible for increased levels of social play.