The Regulation of Endogenous Glutamate and GABA Release from In Vitro Preparations of Rat Striatum

Abstract

The release of the major excitatory and inhibitory neurotransmitters, glutamate and GAB A, from rat caudate-putamen (CP) tissue slices, and GABA release from fetal rat primary striatal cultures, were studied to ascertain key mechanisms underlying the regulation of their release. An improved, highly sensitive method of high performance liquid chromatography and electrochemical detection (LCED) was developed to enable the reliable measurement of these endogenous amino acids from tissue release extracts. The assay permits detection of endogenous amino acids from one milligram of CP tissue in vitro. Release of both amino acids from CP tissue was evoked by elevated levels of potassium, while the potassium channel blocker, 4-aminopyridine (4-AP), selectively released GABA. Glu was selectively released by the excitatory amino acid (EAA) receptor agonist, N-methyl-D-aspartate (NMDA). independently of external Ca2+ concentration. Ca2+<dependent release of Glu and GABA by potassium- and %AP evoked depolarization was shown to be solely dependent on external Ca2+ influx through the P-type Ca2+ channel (P<0.005); blockade of L- and N- types of Ca2+ channels did not reduce release of either amino acid. Potassium and 4-AP also evoked Ca2+ dependent release of GABA from the striatal cultures; GABA was also released by Glu, through a Ca2+-independent process. Activation of D1 dopamine receptors elicited a significant stimulation of GABA release from striatal cultures (P<0.01 1), but no dopaminergic effects were observed on release of either amino acid in CP tissue slices. Potassium (50 %mM KCl) stimulated release of GABA from the cultures was shown to be significantly increased by bicuculline (P<0.05), the GABA(A)receptor antagonist.

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Document Details

Document Type
Technical Report
Publication Date
Jan 01, 1997
Accession Number
ADA439302

Entities

People

  • James B. Phillips Jr

Organizations

  • Uniformed Services University of the Health Sciences

Tags

Communities of Interest

  • Biomedical

DTIC Thesaurus Topics

  • Abstracts
  • Acidic Amino Acids
  • Amines
  • Amino Acids
  • Amino Acids Peptides And Proteins
  • Biomolecules
  • Chemical Compounds
  • Chromatography
  • Dicarboxylic Amino Acids
  • Glutamates
  • Health Services
  • Information Operations
  • Law
  • Liquid Chromatography
  • Potassium
  • Regulations

Fields of Study

  • Biology

Readers

  • Molecular and Cellular Biochemistry
  • Neuroscience