Peripheral nerve stimulation increases serotonin and dopamine metabolites in rat spinal cord.
Extracellular serotonin (5-HT), dopamine (DA), and their metabolites, 5-hydroxyindoleacetic acid (5-HIAA), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA), were assessed in the rat lumbar spinal cord (L3-4) by in vivo microdialysis with high performance liquid chromatography and electrochemical detection (HPLC-ECD). Under urethane-chloralose anesthesia, basal levels of 5-HT and DA in the dialysates were approximately 1.0-1.2 pg/22 microliters sample, 5-HIAA, DOPAC, and HVA were constant at 322.6 +/- 14.9, 8.6 +/- 0.7, and 10.4 +/- 0.4 pg/22 microliters sample (mean +/- SE), respectively. Local application of 100 mM KCl via the dialysis probe increased the 5-HT and DA. Peripheral nerve stimulation that selectively excited the large (A-beta) or small (A-delta) myelinated fibres increased the metabolites. Excitation of the A-beta fibers increased the levels of 5-HIAA to 138%, DOPAC to 155%, and HVA to 143% of the controls. Stimulation of the A-delta fibers increased 5-HIAA to 121%, DOPAC to 120%, and HVA to 124% of the controls. The results suggest that non-nociceptive peripheral nerve stimulation may activate the descending 5-HT and DA systems in the spinal cord.
Men
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Department of Physiology, Showa University School of Dentistry, Tokyo, Japan.
Matsui
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Y
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D006719:Homovanillic Acid / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D017551:Microdialysis; D010525:Peripheral Nerves / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism*
D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D011188:Potassium; D004298:Dopamine; D006719:Homovanillic Acid