Relation of Acetylcholine Release to Ca2+ Uptake and Intraterminal Ca2+ Concentration in Guinea‐Pig Cortex Synaptosomes

Vera Adam‐Vizi, R. H. Ashley

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

Abstract: [14C]Acetylcholine (ACh) release and parallel alterations in 45Ca2+ uptake and intrasynaptosomal free Ca2+concentration ([Ca2+]i) were measured in guinea‐pig brain cortex synaptosomes. Depolarization by high K+ concentrations caused a rapid transient increase in Ca2+ uptake, terminating within 60 s (rate constant = 0.060 s‐1; t1/2= 11.6 s). This resulted in a rapid increase (within 1 s) in [Ca2+]i, which then fell to a maintained but still‐elevated plateau level (t1/2 for the decline was 15 s). Peaks of [Ca2+]ishowed a sigmoidal dependence on depolarization, contrasting with the simple linear dependence of plateau levels of [Ca2+]i. The K+‐evoked ACh release also had two phases: a fast initial increase (t1/2= 11.3 s), which terminated within 60 s, was followed by a slow additional increase during sustained depolarizations of up to 10 min. Depolarization by veratridine led to a slow gradual increase in Ca2+ uptake (t1/2= 130 s) over a 10‐min incubation period, whereas an elevated plateau level of [Ca2+]i was achieved within 2 min (without a rapid peak elevation). The Ca2+‐dependent fraction of the veratridine‐evoked ACh release correlated with the increase in [Ca2+]i rather than with Ca2+ uptake. Using two different methods of depolarization partially circumvented the time limitations imposed by a buffering Ca2+ indicator and we suggest that, in the main, ACh is released in bursts associated with [Ca2+]i transients.

Original languageEnglish
Pages (from-to)1013-1021
Number of pages9
JournalJournal of neurochemistry
Volume49
Issue number4
DOIs
Publication statusPublished - Oct 1987

Keywords

  • Acetylcholine release
  • Cauptake
  • Intraterminal Ca concentration
  • K depolarization
  • Synaptosomes
  • Veratridine

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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