Pain stress and headache

Prolactin signaling modulates stress-induced behavioral responses in a preclinical mouse model of migraine

OBJECTIVE

The aim of this study was to determine if prolactin signaling modulates stress-induced behavioral responses in a preclinical migraine model.

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Stress-Induced Epstein-Barr Virus Reactivation

Epstein-Barr virus (EBV) is typically found in a latent, asymptomatic state in immunocompetent individuals. Perturbations of the host immune system can stimulate viral reactivation. Furthermore, there are a myriad of EBV-associated illnesses including various cancers, post-transplant lymphoproliferative disease, and autoimmune conditions. A thorough understanding of this virus, and the interplay between stress and the immune system, is essential to establish effective treatment. This review will provide a summary of the interaction between both psychological and cellular stressors resulting in EBV reactivation. It will examine mechanisms by which EBV establishes and maintains latency and will conclude with a brief overview of treatments targeting EBV.

Pain and Pain Management Among University Students: Online Survey and Web-Based Education

Pain is common among university students. Unrelieved pain has adverse impacts on their quality of life. In this study, a pain management Web site was developed to distribute an online survey and provide Web-based pain education to university students. Participants were recruited from eight universities in Hong Kong using snowball sampling. The online survey included 37 items examining pain situations, pain management strategies, knowledge about self-medication, and demographic data of the participants. A total of 387 students participated and over 90 percent of them reported pain in the past 6 months. Around one-third of participants did not take any action to manage their pain. Pharmacological method was the most common strategy for students to relieve pain (37.2 percent). The use of over-the-counter (OTC) drug for pain relief was high (n = 214). However, OTC drug knowledge score was significantly higher among health-related group than nonhealth-related group (p < 0.001). There were 188 students who also read the Web-based pain education and completed the evaluation on its usefulness. Nonhealth-related students reported significantly higher scores of self-perceived usefulness for the online education than the health-related students (p < 0.001). Findings suggested the need to consider the service users' background when developing online education program in the future.

Role of spinal GABAA receptor reduction induced by stress in rat thermal hyperalgesia

The mechanisms underlying stress-induced hyperalgesia (SIH) remain poorly understood. Recent findings have provided strong evidence indicating that SIH could be related, at least in part, to alterations in spinal cord GABA activity. In the present study, we first investigated how acute restraint stress impacted pain responses as assessed using the tail flick immersion test. These results showed that rats developed hyperalgesia at 6 h after being subjected to 1-h acute restraint stress. Second, we measured the activation of spinal neurons and alterations in expression of GABAA receptor β2 and β3 subunits as related to stress-induced hyperalgesia. Results from Western blot and immunofluorescence assays showed that c-fos protein increased in the dorsal horn of the lumbar spinal cord and GABAA receptor β2 and β3 subunit proteins decreased significantly at 6 h after exposure to 1 h of acute restraint stress. Finally, the effects of spinal GABAA receptor alteration on SIH were evaluated. These results showed that intrathecal administration of muscimol inhibited hyperalgesia induced by stress while bicuculline enhanced hyperalgesia in the control groups. Taken together, the present data reveal that GABAA receptor β2 and β3 decrease following 1 h of acute restraint stress and may play a critical role in SIH.

Fast-track surgery combined with laparoscopy could improve postoperative recovery of low-risk rectal cancer patients: a randomized controlled clinical trial

OBJECTIVE

In this study we aimed to assess the feasibility and safety of fast-track surgery (FTS) combined with laparoscopy for treating patients with rectal cancer and compare the results with those of the conventional perioperative intervention group.

METHODS

A total of 120 patients with rectal cancer were prospectively randomly assigned to the FTS combined with laparoscopy group and the conventional perioperative intervention plus laparoscopy group from November 2011 to November 2012. All patients received radical anterior resection with total mesorectal excision. Their baseline characteristics and the perioperative outcomes were recorded for analyses.

RESULTS

Compared with the conventional perioperative intervention group, the fast-track protocol combined with laparoscopy could shorten the time to the first flatus (53.44 ± 23.64 h vs 67.85 ± 20.12 h, P = 0.001) and first defecation (65.23 ± 22.24 h vs 86.98 ± 24.85 h, P = 0.000) after operation, accelerate the decrease of white blood cell count (P < 0.05), inhibit body temperature augmentation (P < 0.05) and reduce postoperative complication rate (16.9% vs 3.5%, P = 0.030). In addition, the length of postoperative stay was also shortened (5.05 ± 1.38 days vs 6.98 ± 2.26 days, P = 0.000). The medical cost of hospitalization was also reduced in the FTS group.

CONCLUSION

FTS in combination with laparoscopy may accelerate the clinical recovery of patients with rectal cancer after surgery.

Fast-track surgery could improve postoperative recovery in radical total gastrectomy patients

AIM: To assess the impact of fast-track surgery (FTS) on hospital stay, cost of hospitalization and complications after radical total gastrectomy.

METHODS: A randomized, controlled clinical trial was conducted from November 2011 to August 2012 in the Department of Digestive Surgery, Xijing Hospital of Digestive Diseases, the Fourth Military Medical University. A total of 122 gastric cancer patients who met the selection criteria were randomized into FTS and conventional care groups on the first day of hospitalization. All patients received elective standard D2 total gastrectomy. Clinical outcomes, including duration of flatus and defecation, white blood cell count, postoperative pain, duration of postoperative stay, cost of hospitalization and complications were recorded and evaluated. Two specially trained doctors who were blinded to the treatment were in charge of evaluating postoperative outcomes, discharge and follow-up.

RESULTS: A total of 119 patients finished the study, including 60 patients in the conventional care group and 59 patients in the FTS group. Two patients were excluded from the FTS group due to withdrawal of consent. One patient was excluded from the conventional care group because of a non-resectable tumor. Compared with the conventional group, FTS shortened the duration of flatus (79.03 ± 20.26 h vs 60.97 ± 24.40 h, P = 0.000) and duration of defecation (93.03 ± 27.95 h vs 68.00 ± 25.42 h, P = 0.000), accelerated the decrease in white blood cell count [P < 0.05 on postoperative day (POD) 3 and 4], alleviated pain in patients after surgery (P < 0.05 on POD 1, 2 and 3), reduced complications (P < 0.05), shortened the duration of postoperative stay (7.10 ± 2.13 d vs 5.68 ± 1.22 d, P = 0.000), reduced the cost of hospitalization (43783.25 ± 8102.36 RMB vs 39597.62 ± 7529.98 RMB, P = 0.005), and promoted recovery of patients.

CONCLUSION: FTS could be safely applied in radical total gastrectomy to accelerate clinical recovery of gastric cancer patients.