Brumley Michele R, Hentall Ian D, Pinzon Alberto, Kadam Brijesh H, Blythe Anthony, Sanchez Francisco J, Taberner Annette M, Noga Brian R
The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA.
J Neurophysiol. 2007 Sep;98(3):1440-50. doi: 10.1152/jn.00309.2007. Epub 2007 Jul 18.
Application of neuroactive substances, including monoamines, is common in studies examining the spinal mechanisms of sensation and behavior. However, affected regions and time courses of transmitter activity are uncertain. We measured the spatial and temporal distribution of serotonin [5-hydroxytryptamine (5-HT)] in the lumbosacral spinal cord of halothane-anesthetized adult rats, following its intraspinal microinjection or surface application. Carbon fiber microelectrodes (CFMEs) were positioned at various locations in the spinal cord and oxidation currents corresponding to extracellular 5-HT were measured by fast cyclic voltammetry. Intraspinal microinjection of 5-HT (100 microM, 1-3 microl) produced responses that were most pronounced at CFMEs positioned <or=800 microm from the drug micropipette: 5-HT concentration was significantly higher (1.43 vs. <0.28% of initial concentration) and response latency was shorter (67.1 vs. 598.2 s) compared with more distantly positioned CFMEs. Treatment with the selective 5-HT reuptake inhibitor clomipramine only slightly affected the spread of microinjected 5-HT. Surface application over several segments led to a transient rise in concentration that was usually apparent within 30 s and was dramatically attenuated with increasing depth: 0.25% of initial concentration (1 mM) within 400 microm of the dorsal surface and <0.001% between 1,170 and 2,000 microm. This initial response to superfusion was sometimes followed by a gradual increase to a new concentration plateau. In sum, compared with bath application, microinjection can deliver about tenfold higher transmitter concentrations, but to much more restricted areas of the spinal cord.
包括单胺类在内的神经活性物质在研究感觉和行为的脊髓机制时应用广泛。然而，递质活性的受影响区域和时间进程尚不确定。我们在氟烷麻醉的成年大鼠腰骶部脊髓内微量注射或表面应用血清素[5-羟色胺（5-HT）]后，测量了其空间和时间分布。将碳纤维微电极（CFMEs）置于脊髓的不同位置，通过快速循环伏安法测量与细胞外5-HT相对应的氧化电流。脊髓内微量注射5-HT（100 microM，1 - 3微升）产生的反应在距离药物微滴管≤800微米处的CFMEs最为明显：与位置更远的CFMEs相比，5-HT浓度显著更高（1.43%对<0.28%的初始浓度），反应潜伏期更短（67.1秒对598.2秒）。用选择性5-HT再摄取抑制剂氯米帕明处理仅对微量注射的5-HT的扩散有轻微影响。在几个节段上进行表面应用导致浓度短暂升高，通常在30秒内明显，且随着深度增加显著衰减：在背表面400微米内为初始浓度（1 mM）的0.25%，在1170至2000微米之间<0.001%。这种对灌注的初始反应有时会接着逐渐增加到一个新的浓度平台。总之，与浴槽应用相比，微量注射可输送高出约十倍的递质浓度，但仅限于脊髓的更局限区域。
