期刊
JOURNAL OF NEUROPHYSIOLOGY
卷 98, 期 3, 页码 1440-1450出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.00309.2007
关键词
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资金
- NINDS NIH HHS [R01 NS046404-05, R01 NS046404, R01 NS046404-02, R56 NS046404, R01 NS046404-01A1, R01 NS046404-03, NS-46404, R01 NS046404-04] Funding Source: Medline
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 mu M, 1-3 mu l) produced responses that were most pronounced at CFMEs positioned <= 800 mu m 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 mu m of the dorsal surface and <0.001% between 1,170 and 2,000 mu m. 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.
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