Effects of elevated [K+]0 on the release of neurotransmitters from cortical synaptosomes

Efflux or secretion

J. W. Haycock, W. B. Levy, Larry Denner, C. W. Cotman

Research output: Contribution to journalArticle

126 Citations (Scopus)

Abstract

Elevated K+ 0 elicited a substantial Ca-independent efflux of accumulated GABA from cortical synaptosomal fractions. Efflux from tissue labelled with either NE or choline was affected considerably less by elevated K+ pulses in the absence of calcium. K-facilitated Ca-dependent efflux was large for all three of the accumulated substances. K-dependent (Ca-independent) efflux of accumulated GABA was associated with all subcellular fractions exhibiting GABA accumulation whereas K-facilitated Ca-dependent efflux was restricted to fractions containing synaptosomes. Eighty per cent of both GABA accumulation and K-dependent efflux was, however, recovered in a purified synaptosomal fraction. β-Alanine slightly decreased GABA accumulation, but % K-dependent efflux was not affected. Elevated K+, in the absence of calcium, released GABA from accumulated pools in preference to endogenous pools, whereas the Ca-dependent efflux, facilitated by K+, was similar for both accumulated and endogenous GABA. The Ca-independent efflux of accumulated GABA increased linearly with log [K+]0 between 10 and 70 mM-K+ in sodium-containing media. Prior treatment with veratridine or Na-free medium substantially decreased the Ca-independent but not the Ca-dependent GABA efflux produced by elevated K+ pulses. The Ca-dependent and Ca-independent efflux of accumulated GABA in response to elevated K+ pulses is suggested to arise not only via different flux mechanisms but also from different GABA pools. The Ca-dependent efflux is interpreted to reflect stimulus-secretion coupling process whereas the Ca-independent efflux may reflect membrane transport processes.

Original languageEnglish (US)
Pages (from-to)1113-1125
Number of pages13
JournalJournal of Neurochemistry
Volume30
Issue number5
StatePublished - 1978
Externally publishedYes

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Synaptosomes
gamma-Aminobutyric Acid
Neurotransmitter Agents
Veratridine
Calcium
Subcellular Fractions
Secretory Pathway
Choline
Alanine
Sodium
Tissue
Fluxes
Membranes

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

Cite this

Effects of elevated [K+]0 on the release of neurotransmitters from cortical synaptosomes : Efflux or secretion. / Haycock, J. W.; Levy, W. B.; Denner, Larry; Cotman, C. W.

In: Journal of Neurochemistry, Vol. 30, No. 5, 1978, p. 1113-1125.

Research output: Contribution to journalArticle

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