Ds. Men et Y. Matsui, PERIPHERAL-NERVE STIMULATION INCREASES SEROTONIN AND DOPAMINE METABOLITES IN RAT SPINAL-CORD, Brain research bulletin, 33(6), 1994, pp. 625-632
Extracellular serotonin (5-HT), dopamine (DA), and their metabolites,
5-hydroxyindoleacetic acid (5-HIAA), 3,4-dihydroxyphenylacetic acid (D
OPAC), and homovanillic acid (HVA), were assessed in the rat lumbar sp
inal cord (L3-4) by in vivo microdialysis with high performance liquid
chromatography and electrochemical detection (HPLC-ECD). Under uretha
ne-chloralose anesthesia, basal levels of 5-HT and DA in the dialysate
s were approximately 1.0-1.2 pg/22 mu l sample, 5-HIAA, DOPAC, and HVA
were constant at 322.6 +/- 14.9, 8.6 +/- 0.7, and 10.4 +/- 0.4 pg/22
mu l sample (mean +/- SE), respectively. Local application of 100 mM K
Cl via the dialysis probe increased the 5-HT and DA. Peripheral nerve
stimulation that selectively excited the large (A-beta) or small (A-de
lta) myelinated fibers 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 increa
sed 5-HIAA to 121%, DOPAC to 120%, and HVA to 124% of the controls. Th
e results suggest that nonnociceptive peripheral nerve stimulation may
activate the descending 5-HT and DA systems in the spinal cord.