Faculty Mentor

Dr. Anne Z. Murphy


Morphine is one of the most commonly prescribed medications for the relief of prolonged pain. Both basic science and clinical studies indicate that females require 2-3 times more morphine than males to achieve the same analgesic effect. To date, the mechanisms underlying sex differences in opiate responsiveness are unknown. Recent studies suggest that glial cells are potent modulators of morphine-based analgesia, and in particular, decrease the analgesic effect of opiates. Therefore, we tested the hypothesis that the sexually dimorphic effects of morphine were due to sex differences in glial cell activity. Our studies focused on the midbrain periaqueductal gray (PAG) as this region of the brain is critical for the analgesic effects of morphine. Adult male and female Sprague Dawley rats (250g- 400g) were procured from Charles River Laboratories, and were allowed 7 days to acclimate to the new facility. On the day of the experiment, animals received a subcutaneous injection of morphine (5mg/kg) or were handled in a similar manner. Thirty or 60 minutes after injections or handling, animals were perfused with a 4% paraformaldehyde and 2.5% acrolein tissue fixative solution. Brains were removed and stored in 20% sucrose until ready for sectioning. Brains were sectioned at 25mm using a freezing microtome, and immunohistochemical localization of markers for astrocyte glial cell activity was performed. Antibodies to glial fibrillary acidic protein (GFAP) were used to label activated astrocytes. If our hypothesis is correct, then females will have significantly greater density of the astrocyte cell activity marker GFAP as compared with males. Sex differences in PAG glial cell activity may provide the biological bases for the sexually dimorphic effect of morphine. This research may lead to better treatment for females experiencing prolonged chronic or neuropathic pain.

Cover Page Note

DEDICATION To my family, immediate and extended, whose support is always constant. This would not have come to pass without all your input. Acknowledgements Firstly, I would like to thank Dr. Anne Murphy, my advisor, for allowing me access to the higher level of education offered at the university and pushing me to fulfill my potential. I would like to thank Lori Eidson, whose jedi glia knowledge and advice gave the backbone to this project. I would also like to thank Nicole Victoria, who gave me the fundamental steps needed to start this project. One acknowledgement is not enough, again to the three of you, thank you for your time and effort spent on training, enlightening and preparing me for the bigger picture. Thanks to past and present Murphy lab members for any and all contributions. I would like to thank the Neuroscience Institute and the Biology department. Lastly I would like to thank the GSU Department of Animal Resources, whose time and management allows for the most painless method of learning and care taking of animals.