Date of Award

5-2021

Degree Type

Thesis

Degree Name

Departmental Honors

Department

Biology

Abstract

Oxytocin, a hormone present in the mammalian brain, has been shown to be a vital component of social function in animals and may have a role in the social deficits associated with Autism Spectrum Disorder in humans. Based on previous studies from our lab, there are oxytocin receptors in the human substantia nigra, a basal ganglia structure in the midbrain that is important in both movement and reward pathways. The substantia nigra contains two subsections that are defined by the neurotransmitters they contain: the pars compacta, which is dopaminergic, and the pars reticulata, which is GABAergic. By localizing oxytocin receptors in either the pars compacta or pars reticulata, we can infer the role of that region as it relates to social function. We previously attempted to identify the pars compacta using immunohistochemistry for tyrosine hydroxylase, but the background signal was too high to reliably be used to delineate the boundaries, so we are trying a new approach. We used Nissl staining, which has been shown to reveal dopaminergic neurons in the substantia nigra and has been used to distinguish the pars compacta from the pars reticulata. Once identified, we used the borders of the pars compacta to quantify oxytocin receptors within the substantia nigra in a neuroanatomically informed way by overlaying microscope images of tissue (with the pars compacta outlined) with the receptor autoradiographs, which visualize oxytocin receptors in the substantia nigra. The tissue was acquired from four distinct groups: eight typically developing (TD) males, seven TD females, eight males with Autism Spectrum Disorder, and seven females with Autism Spectrum Disorder. We analyzed the oxytocin receptor binding to determine the effect of sex and autism on oxytocin receptor density in the pars compacta. Females with ASD exhibited significantly reduced OXTR density when compared to both males with ASD and TD females, which may be related to differences in expression of symptoms between males with ASD and females with ASD. Future directions of this research are aimed at defining the role of the oxytocin system in individuals with Autism Spectrum Disorder and how it relates to the social deficits present in those individuals.

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Faculty Mentor

Sara Freeman

Departmental Honors Advisor

Brett Adams