Sex-specific responses to cortical spreading depression: Insights into migraine-associated photophobia and pain
The 2024 MSC Emerging Science Contest for Early-Career Investigators took place on December 9, 2024. Below is a written summary of one of the presentations from the contest. (A recording of the event is available here).
Category: Migraine
Runner up: Manvir Kaur, PhD, University of Arizona
Title: Sex-specific responses to cortical spreading depression: Insights into migraine-associated photophobia and pain.
Hypothesis, methodology, findings and conclusions
Study overview: In this study we investigated how cortical spreading depression (CSD), a mechanism believed to underline migraine with aura, affects photophobia and pain behaviors in a rat model. Our hypothesis was that CSD will cause sex-specific differences in photophobia and pain behavior. Understanding these differences may guide the development of more effective, tailored treatments for migraine patients.
Method: To induce CSD we injected potassium chloride (KCl) or artificial cerebrospinal fluid (aCSF, as a control) into the occipital cortex. We recorded key behavioral assessments including light aversion and dark seeking measured using a three-chamber box, pupil to iris ratio, periorbital tightening, periorbital allodynia and facial withdrawal thresholds.
Key findings: Our findings revealed that female rats responded more strongly to CSD than male rats, demonstrating heightened sensitivity to light (photophobia) and pain (allodynia).
Photophobia: Briefly, KCl-injected females rats spent significantly less time the light box (p=0.001) and more time in the dark chamber (p=0.01) than controls.
Physiological measures: Moreover, females had substantial pupil constriction and eyelid closure at 180 minutes after KCl injection compared to control.
Allodynia: A greater percentage of female rats had periorbital allodynia compared to male rats. Male rats, by contrast, displayed minimal signs of pain or photophobia throughout the experiments.
Conclusion and clinical relevance: Our findings underscore the importance of considering sex-specific differences when developing migraine treatments. By providing a detailed time course of migraine-related behaviors, this study highlights how female physiology may contribute to more intense migraine symptoms. Clinically, this research supports the need for personalized approaches to migraine management, particularly for female patients who experience severe photophobia and pain.
Implications for understanding migraine disease and/or its comorbidities, or how the research holds promise as a new avenue of future migraine study.
Our research has significant implications for understanding migraine disease, particularly the sex-specific mechanisms underlying migraine-associated photophobia and pain. By using a cortical spreading depression (CSD) model in rats, we have discovered significant differences in how male and female physiology responds to this phenomenon. These findings help elucidate why women are disproportionately affected by migraine and often experience more severe symptoms compared to men.
Our research gives insights into sex-specific mechanisms by demonstrating that female rats exhibit heightened sensitivity to light and tactile stimuli (allodynia) following CSD, compared to males. This highlights the role of sex hormones and neural pathways in amplifying migraine symptoms in females, providing insight into the biological factors that contribute to sex disparities in migraine prevalence and severity.
Furthermore, this research provides a foundation for personalized medicine. The sex-specific differences observed in our study underscore the need for personalized approaches to migraine management. Personalized medicine that considers the unique physiological and hormonal factors influencing migraine symptoms in women could significantly improve treatment outcomes.