ISSN:
1432-2013
Keywords:
Crayfish neuromuscular junction
;
Veratridine
;
Excitatory synapse
;
Asynchronous quantal release
;
Quantal store of transmitter
;
Calcium
;
Noise analysis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract At single voltage-clamped opener muscle fibres of crayfish claw, 10–100 μmol/l veratridine increased within a few seconds the rate of asynchronous quantal release, ñ, of excitatory transmitter from ñ〈1 quantum/s to ñ≃10,000 quanta/s. Thereafter ñ declined exponentially either with a single, τ(2)≃50 s, or with two time constants τ(1)≃19 s, τ(2)≃50 s. In total (t→∞), about 0.3 million quanta were released by veratridine in a single short fibre of about 1 mm length. These values were estimated by means of the noise analysis technique and they agreed with equivalent parameters of release when 100 mmol/l K+ were used as release stimulus. Strong quantal release could be elicited only once in a single muscle by veratridine. Furthermore, the effect of veratridine on quantal release could be completely prevented by pretreatment with tetrodotoxin. In another nerve-muscle preparation of crayfish, the abdominal superficial extensor muscle, up to 3 million excitatory quanta could be released by veratridine in a single fibre. In the latter muscle veratridine-induced asynchronous quantal release was strongly dependent on the extracellular concentration of Ca2+ whereas in the claw opener dependence of quantal release on extracellular Ca2+ was negligible.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00585054
Permalink
