RESUMO
Objective: With the aid of an acute visceral pain model of uterine cervical distension (UCD), the present study aimed to observe the effects of intrathecal administration of transient receptor potential vanilloid 1 (TRPV1) antagonist SB-366791 on UCD induced-visceral nociception as well as its involved molecular mechanisms. Methods: A total of 30 Sprague-Dawley-derived adult virgin female rats were used. UCD model was established under isoflurane inhalation anesthesia. Briefly, a lower abdominal incision at midline was made to expose the uteral cervix, two metal rods were inserted through both sides of the cervix separately, one rod was fixed and the other one was connected to a pulley system with application of manual weighted traction (0, 25, 50, 75 or 100 g) for simulating 1 h of cervical distension. In addition, 12 Sprague-Dawley-derived adult virgin female rats were subjected to intrathecal catheter implantation, and UCD was established 7 days later. The rats were divided randomly into two groups; one group was administrated with intrathecal SB-366791 while the other was administrated with the same volume of saline as control. The 75 g distension force was then applied for an hour and the electromyographic (EMG) of musculus rectus abdominis, heart rate as well as respiratory frequency were measured continuously during the surgery. The spinal cord (T(12)-L(2)) was collected 30 minutes after UCD for the detection of changes of c-FOS and TRPV1 expression. Results: UCD increased EMG activity (P<0.05) and c-FOS expression (P<0.05) in the deep dorsal horn region and central canal of the spinal cord (T(12)-L(2)) in a stimuli-dependent manner, the expression of TRPV1 in the T(12)-L(2) spinal cord also increased in response to UCD stimulation (P<0.05). Compared with the saline group, intrathecal SB-366791 significantly decreased EMG activity (P<0.05) as well as spinal c-FOS (P<0.05) expression induced by UCD. Conclusions: UCD in rats increases EMG activity of musculus rectus abdominis as well as spinal c-FOS and TRPV1 expression. Intrathecal administration of TRPV1 antagonist SB-366791 significantly decreases the visceral nociception induced by UCD.
