Department of Neuroscience, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, Texas, USA.
Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA.
Headache. 2022 Jan;62(1):11-25. doi: 10.1111/head.14248. Epub 2021 Dec 29.
The aim of this study was to determine if prolactin signaling modulates stress-induced behavioral responses in a preclinical migraine model.
Migraine is one of the most complex and prevalent disorders. The involvement of sex-selective hormones in migraine pathology is highly likely as migraine is more common in women and its frequency correlates with reproductive stages. Prolactin has been shown to be a worsening factor for migraine. Normally prolactin levels are low; however levels can surge during stress. Dopamine receptor agonists, which suppress pituitary prolactin release, are an effective migraine treatment in a subset of patients. Previously, we showed that administration of prolactin onto the dura mater induces female-specific behavioral responses, suggesting that prolactin may play a sex-specific role in migraine.
The effects of prolactin signaling were assessed using a preclinical migraine model we published recently in which behavioral sensitization is induced by repeated stress. Plasma prolactin levels were assessed in naïve and stressed CD-1 mice (n = 3-5/group) and transgenic mice with conditional deletion of the Prlr in Nav1.8-positive sensory neurons (Prlr conditional knock-out [CKO]; n = 3/group). To assess the contribution of prolactin release during stress, naïve or stressed male and female CD-1 mice were treated with the prolactin release inhibitor bromocriptine (2 mg/kg; n = 7-12/group) or vehicle for 5 days (8-12/group) and tested for facial hypersensitivity following stress. Additionally, the contribution of ovarian hormones in regulating the prolactin-induced responses was assessed in ovariectomized female CD-1 mice (n = 6-10/group). Furthermore, the contribution of Prlr activation on Nav1.8-positive sensory neurons was assessed. Naïve or stressed male and female Prlr CKO mice and their control littermates were tested for facial hypersensitivity (n = 8-9/group). Immunohistochemistry was used to confirm loss of Prlr in Nav1.8-positive neurons in Prlr CKO mice. The total sample size is n = 245; the full analysis sample size is n = 221.
Stress significantly increased prolactin levels in vehicle-treated female mice (39.70 ± 2.77; p < 0.0001). Bromocriptine significantly reduced serum prolactin levels in stressed female mice compared to vehicle-treated mice (-44.85 ± 3.1; p < 0.0001). Additionally, no difference was detected between female stressed mice that received bromocriptine compared to naïve mice treated with bromocriptine (-0.70 ± 2.9; p = 0.995). Stress also significantly increased serum prolactin levels in male mice, although to a much smaller extent than in females (0.61 ± 0.08; p < 0.001). Bromocriptine significantly reduced serum prolactin levels in stressed males compared to those treated with vehicle (-0.49 ± 0.08; p = 0.002). Furthermore, bromocriptine attenuated stress-induced behavioral responses in female mice compared to those treated with vehicle (maximum effect observed on day 4 post stress [0.21 ± 0.08; p = 0.03]). Bromocriptine did not attenuate stress-induced behavior in males at any timepoint compared to those treated with vehicle. Moreover, loss of ovarian hormones did not affect the ability of bromocriptine to attenuate stress responses compared to vehicle-treated ovariectomy mice that were stressed (maximum effect observed on day 4 post stress [0.29 ± 0.078; p = 0.013]). Similar to CD-1 mice, stress increased serum prolactin levels in both Prlr CKO female mice (27.74 ± 9.96; p = 0.047) and control littermates (28.68 ± 9.9; p = 0.041) compared to their naïve counterparts. There was no significant increase in serum prolactin levels detected in male Prlr CKO mice or control littermates. Finally, conditional deletion of Prlr from Nav1.8-positive sensory neurons led to a female-specific attenuation of stress-induced behavioral responses (maximum effect observed on day 7 post stress [0.32 ± 0.08; p = 0.007]) compared to control littermates.
These data demonstrate that prolactin plays a female-specific role in stress-induced behavioral responses in this preclinical migraine model through activation of Prlr on sensory neurons. They also support a role for prolactin in migraine mechanisms in females and suggest that modulation of prolactin signaling may be an effective therapeutic strategy in some cases.
本研究旨在确定催乳素信号是否调节临床前偏头痛模型中的应激诱导行为反应。
偏头痛是最复杂和最常见的疾病之一。偏头痛病理中涉及选择性激素的可能性很高，因为偏头痛在女性中更为常见，其频率与生殖阶段相关。催乳素已被证明是偏头痛恶化的一个因素。通常催乳素水平较低；然而，在应激期间，水平会激增。多巴胺受体激动剂抑制垂体催乳素释放，对一部分偏头痛患者有效。先前，我们表明将催乳素施用于硬脑膜会引起女性特异性行为反应，这表明催乳素可能在偏头痛中发挥性别特异性作用。
我们最近发表了一种临床前偏头痛模型，该模型通过重复应激诱导行为敏化，用于评估催乳素信号的作用。在幼稚和应激的 CD-1 小鼠（每组 n = 3-5）和 Nav1.8 阳性感觉神经元中条件性缺失 Prlr 的转基因小鼠（Prlr 条件性敲除 [CKO]；每组 n = 3）中评估血浆催乳素水平。为了评估应激期间催乳素释放的贡献，用催乳素释放抑制剂溴隐亭（2mg/kg；每组 n = 7-12）或载体处理幼稚或应激的雄性和雌性 CD-1 小鼠 5 天（每组 8-12），并在应激后测试面部过敏。此外，还评估了卵巢激素在调节催乳素诱导的反应中的作用，方法是将去卵巢的雌性 CD-1 小鼠（每组 n = 6-10）。此外，还评估了 Prlr 在 Nav1.8 阳性感觉神经元上的激活作用。用溴隐亭或载体处理幼稚或应激的雄性和雌性 Prlr CKO 小鼠及其对照同窝仔鼠，测试面部过敏（每组 n = 8-9）。免疫组织化学用于确认 Prlr 在 Prlr CKO 小鼠的 Nav1.8 阳性神经元中的缺失。总样本量为 n = 245；完整分析样本量为 n = 221。
应激显著增加了载体处理的雌性小鼠的催乳素水平（39.70 ± 2.77；p < 0.0001）。溴隐亭显著降低了应激雌性小鼠与载体处理小鼠相比的血清催乳素水平（-44.85 ± 3.1；p < 0.0001）。此外，与接受溴隐亭处理的幼稚小鼠相比，接受溴隐亭处理的应激雌性小鼠之间没有差异（-0.70 ± 2.9；p = 0.995）。应激也显著增加了雄性小鼠的血清催乳素水平，但程度远低于雌性（0.61 ± 0.08；p < 0.001）。溴隐亭显著降低了应激雄性与载体处理雄性相比的血清催乳素水平（-0.49 ± 0.08；p = 0.002）。此外，与载体处理相比，溴隐亭减轻了应激诱导的雌性小鼠的行为反应（最大效应观察到应激后第 4 天[0.21 ± 0.08；p = 0.03]）。与载体处理相比，溴隐亭在任何时间点均未减轻雄性应激诱导的行为反应。此外，与应激的去卵巢手术小鼠相比，卵巢激素的丧失并不影响溴隐亭与载体处理相比减轻应激反应的能力（最大效应观察到应激后第 4 天[0.29 ± 0.078；p = 0.013]）。与 CD-1 小鼠相似，应激增加了 Prlr CKO 雌性小鼠（27.74 ± 9.96；p = 0.047）和对照同窝仔鼠（28.68 ± 9.9；p = 0.041）的血清催乳素水平，与它们的幼稚对应物相比。未检测到应激诱导的雄性 Prlr CKO 小鼠或对照同窝仔鼠的血清催乳素水平显著增加。最后，Nav1.8 阳性感觉神经元中 Prlr 的条件性缺失导致应激诱导的行为反应呈雌性特异性减弱（最大效应观察到应激后第 7 天[0.32 ± 0.08；p = 0.007]）与对照同窝仔鼠相比。
这些数据表明，催乳素通过激活感觉神经元上的 Prlr 在这个临床前偏头痛模型中发挥应激诱导行为反应的性别特异性作用。它们还支持催乳素在女性偏头痛机制中的作用，并表明调节催乳素信号可能是某些情况下的有效治疗策略。
