Meningeal prolactin signaling and female-selective migraine mechanisms

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Women consistently report higher headache-related disabilities, higher relapse rate, more frequent, longer lasting, and more severe headaches than men. Hence, there is an urgent need to customize migraine management schemes based on sex-specific pain mechanisms. Accordingly, our long-term goal is to define sex-specific mechanisms of migraine, and utilize this knowledge to provide more effective sex- based personalized migraine management schemes. It is well accepted that the pathogenesis of headache syndromes, especially migraine, are sex-dependent due to important contributions of gonadal hormones (GnH). First, some reports show that migraine attacks in female and males are accompanied by a rise in plasma levels of prolactin (PRL). Second, we and others demonstrated that PRL responsiveness in pain pathways is sex-dependent and strictly controlled by estrogen. There is a critical gap in knowledge pertaining to whether and how the PRL system sex- dependently regulates migraine. The objective of this proposal is to identify mechanisms linking the PRL system to stress- and sex-dependent regulation of certain types of migraine. Our preliminary data demonstrate that PRL applied to cranial dura induces long-lasting facial allodynia in females, but not males. PRL also sensitizes mustard oil-evoked CGRP release from female, but not male dura. Finally, to further link the PRL system to migraine, we showed that a PRL receptor (Prlr) antagonist blocks CGRP- induced migraine behavior in females. Thus, our central hypothesis is that PRL acting through the Prlr on dural-innervating sensory neurons mediates female-specific mechanisms contributing to migraine. The rationale for the proposed study is that it 1) greatly expands our knowledge of sex differences in migraine mechanisms; and 2) provides translational potential by offering therapeutic targets for sex-based migraine management. Our hypothesis is tested by interconnected yet independent aims. Aim 1 examines sex-specific expression and regulation of PRL and Prlr in the trigemino-vascular system. Aim 2 determines how PRL and Prlr sex-specifically modulate the activity of dural afferents and migraine- like behavior in stress-induced migraine models. Aim 3 assesses a link between CGRP-induced migraine behavioral responses and the dural PRL system. The proposed study is innovative since it defines conceptually novel sex-specific regulatory mechanisms for certain migraine models based on PRL signaling. The proposed research is significant as it advances our understanding of sex differences in migraine mechanisms – an understudied area where increasing basic science knowledge has the potential to lead to better sex-based personalized therapeutics.