Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1998-5-5
pubmed:abstractText
1. Oxytocin and vasopressin secretion from the neurohypophysis (NHP) is evoked by strongly patterned bursts of action potentials. We studied excitation-secretion coupling in single isolated terminals of rat NHP using patch clamp and capacitance detection techniques. 2. The secretory response evoked by trains of depolarizing pulses consisted of two discrete phases. Ca2+ entry during pulses early in the train did not elicit secretion. Exocytotic responses began only after a characteristic amount of total Ca2+ entry called "threshold". 3. In the postthreshold secretory phase, exocytotic events occurred during or immediately after depolarizing pulses, indicating that the final Ca(2+)-dependent step is triggered by high Ca2+ concentrations near the plasma membrane that dissipate rapidly after channel closure. Secretion was sensitive to both the concentration and species of Ca2+ chelator. BAPTA, a Ca2+ chelator with rapid Ca2+ binding kinetics, was more effective than EGTA in diminishing secretion. 4. The "threshold" amount of Ca2+ was determined by the concentration, but not species, of Ca2+ chelator. The threshold value was constant even when Ca2+ entry parameters were varied over a broad range of current amplitudes, pulse durations, and number of pulses, indicating that it did not require high Ca2+ concentrations near the plasma membrane. 5. These results suggest that the secretory response to a train of pulses consists of a Ca(2+)-dependent preparatory step that must be completed before subsequent Ca2+ entry can elicit exocytosis. 6. Exocytotic responses during single trains showed strong depression at a step subsequent to Ca2+ entry. Recovery from depression required 30-60 sec. 7. The properties of threshold secretion observed in NHP terminals are discussed in terms of current models of secretion.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0272-4340
pubmed:author
pubmed:issnType
Print
pubmed:volume
18
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
65-80
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Excitation-secretion coupling in mammalian neurohypophysial nerve terminals.
pubmed:affiliation
Department of Neurobiology and Anatomy, Allegheny University, Philadelphia, Pennsylvania 19129, USA.
pubmed:publicationType
Journal Article, Comparative Study