HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bracho, H. Articles by Orkand, R. K. Search for Related Content PubMed PubMed Citation Articles by Bracho, H. Articles by Orkand, R. K.

1. The effects of varying the external Ca concentration from 1·8 to 30 mM/l. (-2 times normal) have been studied at the in vitro crayfish excitatory neuromuscular junction. Electrophysiological techniques were used to record transmembrane junctional potentials from muscle fibres and extracellular junctional currents from the vicinity of nerve terminals.

2. The excitatory junctional potential amplitude was proportional to [Ca]₀ⁿ, where n varied between 0·68 and 0·94 (mean 0·82) when [Ca]₀ was varied from 1·8 to 15 mM/l.

3. The increase in junctional potential amplitude on raising [Ca]₀ resulted primarily from an increase in the average number of quanta of excitatory transmitter released from the presynaptic nerve terminal by the nerve impulse.

4. The size of the quanta, synaptic delay, presynaptic potential and electrical properties of the muscle membrane were little affected by changes in calcium concentration in the range studied.