鞘内注射氯胺酮对神经痛大鼠背根神经节细胞内钙含量的影响

Effect of intrathecal ketamine on the calcium ion concentration in the spinal dorsal root ganglion neurons in a rat model of chronic neuropathic pain

目的探讨鞘内注射氯胺酮对慢性坐骨神经挤压损伤(CCI)大鼠脊髓背根神经节(DRG)细胞内Ca2+含量([Ca2+]i)的影响。方法雄性SD大鼠36只,随机分为3组(n=12):假手术组(Ⅰ组);CCI组(Ⅱ组);氯胺酮组(Ⅲ组)。Ⅲ组于CCI术前30min、术后1、2、3、5、7、9、11d鞘内注射氯胺酮1mg/kg,Ⅰ、Ⅱ组注射等量生理盐水。分别以vonFrey纤维丝和冷水测定触痛阈值及冷刺激反应。术后7、14d断头取L4-6双侧DRG,以流式细胞仪测定脊髓DRG细胞[Ca2+]i。结果与Ⅰ组比较,Ⅱ组术后7d术侧触痛阈值下降,冷刺激反应升高,Ⅱ组、Ⅲ组术后14d术侧触痛阈值下降,冷刺激反应升高(P<0.01或0.05);与Ⅱ组相比,Ⅲ组术后7、14d术侧触痛阈值升高,冷刺激反应降低(P<0.05)。与Ⅰ组相比,Ⅱ组术后7d双侧、Ⅱ组和Ⅲ组术后14d术侧脊髓DRG细胞[Ca2+]i升高;与Ⅱ组比较,Ⅲ组术后7d双侧及术后14d术侧脊髓DRG细胞[Ca2+]i明显降低(P<0.05或0.01)。结论鞘内注射氯胺酮治疗慢性神经痛可能与拮抗NMDA受体进而抑制脊髓DRG细胞[Ca2+]i升高有关。

Objective To investigate the effect of intrathecal ketamine on the intracellular calcium ion concentration [Ca2+ ]1 in the spinal dorsal root ganglion (DRG) neurons in a rat model of chronic neuropathic pain produced by chronic constrictive injury (CCI) .Methods Thirty-six male SD rats weighing 160-180 g were randomly divided into 3 groups ( n = 12 each) : Ⅰ sham-operated group; Ⅱ CCI group and Ⅲ ketamine + CCI group. The animals were anesthetized with intraperitoneal pentobarbital 40 mg·kg-1 . The right sciatic nerve was exposed and 4 loose ligatures were placed on the trunk of the nerve at 1-2 mm interval. In sham-operated group (Ⅰ) the sciatic nerve was exposed but not ligated. Intrathecal catheter was implanted at L4,5 and correct placement was confirmed by aspiration of cerebro-spinal fluid. In group Ⅲ ketamine 1 mg · kg-1 was administered intrathecally. 30 min before and on the 1st, 2nd, 3rd, 5th, 7th, 9th and 11th day after operation. In group Ⅰ and Ⅱ normal saline (NS) was given intrathecally instead of ketamine. Thermal and mechanical hyperalgesia were measured with ice-cold water and von-Frey filaments on the 7th and 14th day after operation. The animals were killed by cervical dislocation on the 7th (n = 6) and 14th ( n = 6) day. Bilateral DRG of L4-6 spinal nerve were removed and homogenized and centrifuged at 5 000 r/min. DRG neurons were isolated and [ Ca2+ ] i was measured by flow cytometry.Results In group Ⅱ (CCI) pain threshold to von-Frey hair stimulation decreased by 80.3% (on the 7th day) and 84.8% (14th day) while pain threshold to noxious thermal stimulation increased by 309.4% (the 7th day) and 336.2% (14th day) (P < 0.01) as compared to sham-operated group ( Ⅰ ) . In group Ⅲ (ketamine + CCI group) Ppain threshold to von-Frey hair stimulation decreased by 24.1% (the 7th day) and 52.7% (the 14th day) while pain threshold to cold water stimulation increased by 78.8% and 100.0% respectively compared to group Ⅰ . The differences in pain threshold between the groups were statistically significant. In group Ⅱ (CCI) the [Ca2+ ]i in DRG neurons increased by 71.7% and 17.6% on the 7th and 14th day after operation on the left side and by 75.4% and 165.8% respectively on the operated side compared to group Ⅰ (sham-operated); whereas in group Ⅲ (ketamine + CCI) the [Ca2+ ]i in DRG neurons increased by 19.1% and 5.7% on the left side and 23.6% and 63.9% on the operated side compared to group Ⅰ .Conclusion The antinociceptive effect of intrathecal ketamine may be associated with NMDA receptor and suppression of increases in [Ca2+ ]i in the DRG neurons.