Miranda Adrian, Peles Shachar, Rudolph Colin, Shaker Reza, Sengupta Jyoti N
Department of Pediatrics, Medical College of Wisconsin, Milwaukee, 53226, USA.
Gastroenterology. 2004 Apr;126(4):1082-9. doi: 10.1053/j.gastro.2004.01.003.
BACKGROUND & AIMS: Patients with fibromyalgia commonly have symptoms of abdominal pain, suggesting that altered somatic afferent activity may influence visceral sensations. It is hypothesized that a noxious somatic stimulus increases input to the projection neurons in the dorsal horn, resulting in visceral hyperalgesia.
Two injections (100 microL, pH 4.0) were given unilaterally in the gastrocnemius muscle 2 days apart in male Sprague-Dawley rats. Paw withdrawal reflex (PWR) was measured to assess somatic pain. The control group received pH 7.2 saline injections. Similar injections (pH 4.0) were given in the front leg in a different group. Electromyography (EMG) from the external oblique muscle was recorded to graded colorectal distention at different time intervals. NMDA receptor antagonist (CGS-19755, 20 nmol) or AMPA/kainate receptor antagonist (NBQX, 20 nmol) was injected intrathecally before low-pH injections.
A bilateral decrease in PWR threshold occurred 72 hours after the second low-pH injection. There was no decrease in the threshold in rats injected with pH 7.2 saline. A significant increase in EMG to colorectal distention (> or =30 mm Hg) occurred at 72 hours and 2 weeks in the pH 4.0 group. No change in EMG was observed following 2 unilateral low-pH injections in the front leg. Both the visceral hyperalgesia and the decrease in somatic pain thresholds were prevented by prior intrathecal CGS-19755 or NBQX injections.
Noxious somatic afferent input from the hind limb facilitates visceral hyperalgesia, which is due to viscerosomatic convergence in the lower spinal cord. This can be blocked by ionotropic glutamate receptor antagonists.
纤维肌痛患者常伴有腹痛症状，提示躯体传入活动的改变可能影响内脏感觉。据推测，有害的躯体刺激会增加背角投射神经元的输入，从而导致内脏痛觉过敏。
在雄性Sprague-Dawley大鼠的腓肠肌单侧注射两次（100微升，pH 4.0），间隔2天。测量爪部退缩反射（PWR）以评估躯体疼痛。对照组接受pH 7.2的生理盐水注射。另一组在前肢进行类似注射（pH 4.0）。记录不同时间间隔下腹外斜肌的肌电图（EMG）对结肠扩张的反应。在低pH值注射前鞘内注射NMDA受体拮抗剂（CGS-19755，20纳摩尔）或AMPA/海人藻酸受体拮抗剂（NBQX，20纳摩尔）。
第二次低pH值注射72小时后，PWR阈值双侧降低。注射pH 7.2生理盐水的大鼠阈值未降低。pH 4.0组在72小时和2周时，对结肠扩张（≥30毫米汞柱）的EMG显著增加。在前肢进行两次单侧低pH值注射后，未观察到EMG变化。鞘内预先注射CGS-197*********
