Repeated spinal cord stimulation decreases the extracellular level of γ-aminobutyric acid in the periaqueductal gray matter of freely moving rats

Carl Olav Stiller, Bengt Linderoth, William T. O'Connor, Johan Franck, Torkel Falkenberg, Urban Ungerstedt, Ernst Brodin

Research output: Contribution to journalArticlepeer-review

Abstract

Most of the previous experimental studies on the antinociceptive effects of electrical spinal cord stimulation (SCS) have focused on short-lasting effects mainly depending on spinal mechanisms. However, patients treated with SCS for chronic pain often report pain relief exceeding the period of stimulation for several hours. The long lasting effect of SCS might not only involve spinal, but also supraspinal mechanisms. A supraspinal region of major importance for the coordination of descending pain inhibition is the periaqueductal grey matter (PAG). The aim of the present microdialysis study, performed in awake freely moving rats, was to investigate if repeated SCS (two 30 min periods separated by a 90 min resting period) alters the extracellular neurotransmitter concentrations in the ventrolateral PAG. In a first series of experiments significantly decreased (-30%;P < 0.05;n = 7) γ-aminobutyric acid (GABA) levels were detected immediately after the second SCS session. Neither the concentration of serotonin nor that of substance P-like immunoreactivity (SP-LI) was affected by SCS. The decrease of GABA after two SCS sessions was confirmed in a second series of experiments (-30%;P < 0.05;n = 7). No spontaneous decline of GABA was observed in sham-stimulated animals (n = 6). The glutamate concentration was also determined in this latter series of experiments and a significant decrease (-23%;P < 0.05;n = 5) was observed after the second SCS session. As GABA-neurons in the PAG exert a tonic depressive effect on the activity in descending pain inhibitory pathways, a decreased extracellular GABA level in this region, as detected following repeated SCS, might indicate an increased pain inhibition.

Original languageEnglish
Pages (from-to)231-241
Number of pages11
JournalBrain Research
Volume699
Issue number2
DOIs
Publication statusPublished - 20 Nov 1995
Externally publishedYes

Keywords

  • 5-Hydroxytryptamine
  • Glutamate
  • Microdialysis
  • Periaqueductal gray matter
  • Rat
  • Spinal cord stimulation
  • Substance P
  • γ-Amino-butyric-acid

Fingerprint

Dive into the research topics of 'Repeated spinal cord stimulation decreases the extracellular level of γ-aminobutyric acid in the periaqueductal gray matter of freely moving rats'. Together they form a unique fingerprint.

Cite this