Date of Award

Fall 12-13-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Science

First Advisor

Dr. Godwin Ananaba

Second Advisor

Dr. Ketema Paul

Third Advisor

Dr. Nathan Bowen

Abstract

The Dorsal Raphe Nucleus (DRN) is a complex brain region that has been implicated in disorders such as anxiety and depression. The DRN is divided into subregions through its rostrocaudal and mediolateral axis. It has been reported that after a single restraint session there is differential spatial activation of nitric oxide synthase (NOS) across the DRN. The temporal profile of NOS activity during acute stress is not known but it is important because duration of acute stress is associated with different general responses. In this report rats were restrained for 1, 3, or 6 hours and nicotinamide adenine phosphate diaphorase (NADPH-d) was stained as an index to NOS activity to determine the spatio-temporal profile of NOS throughout a 6 hour restraint. Astrocyte reactivity was also measured to determine whether NOS activation correlated with GFAP expression since astrocytes react to neural activity and store and release l-arginine, the precursor for nitric oxide production. The results showed that the DRN had a dynamic response to acute restraint stress, most notably in the caudal lateral wings where activation increased after 3 hours of restraint (p = > 0.001) but neuron count decreased after 6 hours (p = 0.040). Astrocytes did not correlate with NOS activation but they showed spatio-temporal differences as well whereas they were more active in the rostral half of the DRN. In conclusion, the present study suggests that NOS produced in the DRN may have a role in prolonged exposure to acute stress and that subregions show differential NOS activation.

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