Date of Award
Spring 2024
Rights
Access is available to all users
Document Type
Thesis
Degree Name
Master of Science (MS) in Biology
Department
Biology
Abstract
The striatum is highly innervated by dopamine neurons and is involved in movement control (dorsal striatum) reward learning (ventral striatum). Fast-scan cyclic voltammetry (FSCV) is a technique that uses microelectrodes (diameter ~5 μm, length ~150 μm) to monitor dopamine signaling in the brain. Although urethane and isoflurane anesthetics are commonly used in in vivo studies, isoflurane’s potential influence on dopamine signaling has not been thoroughly investigated. In addition to this, the addictive nature of nicotine indicates the importance of understanding its impact of dopamine neurotransmission within the different striatal subregions. Male Sprague-Dawley rats (Rattus norvegicus) 300 – 450 grams were anesthetized with isoflurane or urethane anesthesia. Once fully anesthetized, rats were secured in a stereotaxic apparatus, skin and fascia were removed, and small holes (diameter 1-2 mm) were drilled in the skull for microelectrode placement. The reference electrode was placed just below dura, FSCV electrode was placed in the dorsal striatum, and stimulating electrode was placed above the medial forebrain bundle. Biphasic pulses (60 Hz, 60 pulses, 300μA) were sent through the bipolar stimulating electrode to evoke dopamine release. Electrodes were lowered, and optimized, until clear dopamine signals were evoked. Once clear and stable dopamine signals were recorded, isoflurane (n = 5) and urethane (n = 7) anesthetized rats were injected with saline (control) according to body weight. Additionally, another group of urethane anesthetized rats were treated with 0.8 mg/kg of nicotine (n = 6). Dopamine signals were stimulated and recorded for 1 hour after i.p. injection. Post surgery, electrolytic lesions were created at the tip of the FSCV electrode for electrode placement analysis. These data indicated no difference between isoflurane and urethane anesthetics in FSCV recording of dopamine. Interestingly, nicotine significantly decreased electrically evoked dopamine signals 5 – 55 minutes post nicotine injection compared to saline-treated controls. Furthermore, kinetic analysis revealed a significant decrease in upward velocity (dopamine release) and a significant increase in downward velocity (dopamine uptake) 5 – 30 minutes post nicotine injection. Lastly, lesioning studies suggest that 45 sec lesions and flash freezing brains in 2-methylbutane resulted in clear and visible electrode placements within the dorsal striatum.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Rosenbaum, Gracie E., "The influence of anesthesia and nicotine on dopamine signaling in the rat dorsal striatum" (2024). EWU Masters Thesis Collection. 943.
https://dc.ewu.edu/theses/943
