γ-Aminobutyric acid inhibits the potassium-stimulated release of somatostatin from rat spinal cord slices

Michael R. Vasko, Virginia Harris

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Evidence supports the idea that somatostatin (SO) is a neurotransmitter or neuromodulator of primary afferent neurons involved in nociception. Since γ-aminobutyric acid (GABA), norepinephrine, and morphine alter nociception at the level of the spinal cord, we examined whether these agents could alter the potassium-stimulated release of somatostatin from rat spinal cord slices. Male Sprague-Dawley rats were decaptitated and a 2 cm segment of the lumbar spinal cord removed and chopped into 0.5 × 0.5 mm pieces and perfused at 37 °C in individual perfusion chambers with a modified Krebs-bicarbonate buffer at a flow rate of 0.5 ml/min. Perfusates were collected at 2 min intervals and assayed for SO using radioimmunoassay. Exposure of spinal cord tissue to 50 mM KCl resulted in a 3-fold increase in release of SO from a basal level of approximately 0.2 to 0.6 pg/mg tissue/min. This evoked release was calcium dependent. Pre-exposure of tissue to GABA at 10-4 and 10-5 M significantly inhibited the potassium-stimulated release of SO, but did not alter basal release. The GABA receptor antagonist, bicuculline methiodide, at 10-5 but not 10-6 M attenuated the GABA-induced inhibition of somatostatin release. Bicuculline methiodide alone did not significantly alter either basal or stimulated release. Neither baclofen (10-5 M, 5 × 10-5 M), norepinephrine (10-5 M), nor morphine (10-5 M) had any significant effect on basal or stimulated release of SO from spinal cord tissue. These results demonstrate a differential regulation of SO release from spinal cord tissue, but do not support the hypothesis that inhibition of SO release in the spinal cord is a mechanism to explain antinociception produced by GABA agonists, norepinephrine or morphine at the level of the spinal cord.

Original languageEnglish (US)
Pages (from-to)129-137
Number of pages9
JournalBrain research
Volume507
Issue number1
DOIs
StatePublished - Jan 15 1990

Keywords

  • Baclofen
  • Bicuculline
  • Morphine
  • Norepinephrine
  • Release
  • Somatostatin
  • γ-Aminobutyric acid

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

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