Marsala M, Malmberg A B, Yaksh T L
Department of Anesthesiology, University of California at San Diego, La Jolla 92093, USA.
J Neurosci Methods. 1995 Nov;62(1-2):43-53. doi: 10.1016/0165-0270(95)00053-4.
To permit long-term measurement of time-dependent changes in levels of dialyzable drugs and transmitters in the spinal intrathecal (i.t.) space of the unanesthetized rat, we developed a dialysis catheter for chronic placement. This was accomplished by constructing a loop probe 9 cm in length from 0.3-mm-diameter dialysis tubing that was made impermeable except for the distal loop. This loop catheter was readily inserted though an incision in the cisternal membrane and passed to the lumbar enlargement. The ends of the catheter were then externalized on the top of the head. To permit i.t. injections, an additional i.t. catheter could also be inserted simultaneously by the same route. For dialysis, an external end of the loop catheter was connected to a syringe pump and perfused with artificial CSF (10 microliters/min) and the out flow collected. A series of studies were performed to demonstrate the characteristics and utility of this technique. (1) Stability of resting release: glutamate and glucose concentrations in spinal dialysate showed no significant changes from 3 to 10 days after implantation. (2) Spinal cord ischemia: ischemia induced by aortic occlusion or cardiac arrest evoked a time dependent increase in retrieved glutamate. (3) Spinal cord compression caused a time-dependent glutamate, aspartate and PGE2 increase. (4) Noxious afferent stimulation induced by the injection of formalin into the hindpaw resulted in a rapid and transient increase in dialysate glutamate concentration. (5) Direct activation of spinal excitatory amino acids receptors by i.t. injection of kainic acid (1 microgram) evoked a significant increase in aspartate and taurine. (6) Continuous delivery of spinal opiate (alfentanil) via dialysis resulted in a maintained, concentration dependent elevation in the thermal escape latencies in the unanesthetized rat. The loop dialysis catheter provides a robust experimental tool for studying time dependent changes in the concentration of diffusible substances in spinal CSF over an extended post-implantation interval and allows comparison of these changes with concurrently assessed behavioral indices.
为了长期测量未麻醉大鼠脊髓鞘内（i.t.）空间中可透析药物和递质水平随时间的变化，我们开发了一种用于长期植入的透析导管。这是通过用直径0.3毫米的透析管构建一个9厘米长的环形探头来实现的，除了远端环外，该透析管都做了防渗处理。这个环形导管很容易通过小脑延髓池膜上的切口插入，并延伸至腰膨大处。然后将导管的两端引出到头顶。为了便于进行鞘内注射，还可以通过相同途径同时插入一根额外的鞘内导管。进行透析时，将环形导管的一个外端连接到注射泵，并用人造脑脊液（10微升/分钟）进行灌注，同时收集流出液。我们进行了一系列研究以证明该技术的特性和实用性。（1）静息释放的稳定性：植入后3至10天，脊髓透析液中的谷氨酸和葡萄糖浓度无显著变化。（2）脊髓缺血：主动脉闭塞或心脏骤停引起的缺血导致回收的谷氨酸随时间增加。（3）脊髓压迫导致谷氨酸、天冬氨酸和前列腺素E2随时间增加。（4）后爪注射福尔马林引起的有害传入刺激导致透析液谷氨酸浓度迅速短暂升高。（5）鞘内注射 kainic 酸（1微克）直接激活脊髓兴奋性氨基酸受体，引起天冬氨酸和牛磺酸显著增加。（6）通过透析持续输送脊髓阿片类药物（阿芬太尼）导致未麻醉大鼠的热逃避潜伏期持续升高，且呈浓度依赖性。环形透析导管为研究植入后较长时间内脊髓脑脊液中可扩散物质浓度随时间的变化提供了一个强大的实验工具，并允许将这些变化与同时评估的行为指标进行比较。
