Effects of potassium, veratridine, and scorpion venom on calcium accumulation and transmitter release by nerve terminals in vitro.

Blaustein, M. P.

doi:10.1113/jphysiol.1975.sp010950

Cited by 551 publications

(329 citation statements)

References 60 publications

Supporting

Mentioning

293

Contrasting

Unclassified

Order By: Relevance

“…The increased calcium influx into nerve terminals associated with the process of depolarization is only seen when the potassium concentration is increased above 15 to 20 mm (Blaustein, 1975) Evidence for the suggestion that the sodiumdependent uptake of [:'H]-spermine at low concentrations may be associated with a possible transmitter pool was examined by measuring the K+-stimulated release of spermine from rat cerebral cortex slices which had been labelled with [:'H]-spermine in the absence of sodium. The release of spermine following uptake in a sodium-free medium was decreased by 66%, a value which again closely corresponds to the degree of inhibition observed when perfusions were performed in a calcium-free medium.…”

Section: Discussionmentioning

confidence: 99%

THE SPONTANEOUS AND EVOKED RELEASE OF SPERMINE FROM RAT BRAIN in vitro

Harman

Shaw

1981

British J Pharmacology

View full text Add to dashboard Cite

The efflux of previously accumulated [3H]‐spermine from brain slices was measured using a continuous perfusion system. The spontaneous efflux was biphasic, consisting of an initial rapid efflux followed by a much slower release. The slices were depolarized by the addition to the medium of high potassium concentrations, ouabain or veratrine. At concentrations greater than 30 mM, potassium evoked a striking increase in the release of [3H]‐spermine. Following uptake in the presence of 5.7 × 10−9M[3H]‐spermine, K+‐evoked release was dependent on the presence of calcium ions. Release of spermine after uptake at 5.6 × 10−8m or 5.0 × 10−7m was not calcium‐dependent. The calcium‐dependent, K+‐stimulated release of spermine was inhibited in the presence of diphenylhydantoin (5 × 10−3m) or ruthenium red (10−3 m). Following uptake of 5.7 × 10−9m [3H]‐spermine in a sodium‐free medium, the calcium‐dependent, K+‐stimulated release was significantly inhibited. Ouabain (10−4m) caused a large but calcium‐independent increase in the efflux of [3H]‐spermine. Veratrine‐induced release was less substantial but was increased in a calcium‐free medium. Release evoked by veratrine was abolished in the absence of sodium. These results are discussed with respect to a possible ‘neurotransmitter’ or ‘neuromodulator’ role for spermine.

show abstract

Section: Discussionmentioning

confidence: 99%

THE SPONTANEOUS AND EVOKED RELEASE OF SPERMINE FROM RAT BRAIN in vitro

Harman

Shaw

1981

British J Pharmacology

View full text Add to dashboard Cite

show abstract

“…6). Hence it is plausible that AcCho liberation, triggered in vivo and in vitro by an increased level of free Ca2+ in the nerve ending's cytoplasm (7)(8)(9), is accompanied by the phosphorylation of specific proteins. Krueger et al (10) have shown that agents which increase Ca2+ transport into intact rat brain synaptosomes stimulate the incorporation of 32P, into synaptosomal proteins of apparent subunit molecular weights of 80,000 and 86,000.…”

mentioning

confidence: 99%

Mechanism of acetylcholine release: possible involvement of presynaptic muscarinic receptors in regulation of acetylcholine release and protein phosphorylation.

Michaelson¹,

Avissar²,

Kloog³

et al. 1979

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Acetylcholine (AcCho) release from purely cholinergic Torpedo synaptosomes was evoked by K+ depolarization in the presence of Ca2+. Activation of muscarinic receptors, present in the synaptosomal fraction, by the agonist oxotremorine resulted in the inhibition of AcCho liberation. This inhibition was abolished by the muscarinic antagonist atropine, which by itself has no effect. These findings suggest that the muscarinic receptor, present in the electric organ of Torpedo, is presynaptic and that its physiological function is to regulate AcCho release by negative feedback. The mechanism of presynaptic muscarinic inhibition was investigated by examining the effect of muscarinic ligands on synaptosomal 45Ca2+ uptake and on the level of phosphorylation of specific synaptosomal proteins. Ca2+-dependent K+ depolarization-induced synaptosomal AcCho release was accompanied by 45Ca2+ uptake and by a marked increase in the phosphorylation of a specific synaptosomal protein (band a) of approximately 100,000 daltons. Activation of the muscarinic receptor by the agonist oxotremorine had no detectable effect on synaptosomal 45Ca2+ uptake but resulted in the concomitant inhibition of AcCho release and of phosphorylation of band a. The muscarinic antagonist atropine abolished the inhibitory effect of oxotremorine both on AcCho liberation and on phosphorylation of band a. These findings suggest that phosphorylation of band a may be involved in regulation of the presynaptic processes that underly AcCho release and that activation of the muscarinic receptor' by agonists may inhibit AcCho release by blocking the phosphorylation of band a.It has been suggested that some cholinergic synapses contain presynaptic muscarinic receptors which regulate the extent of acetylcholine (AcCho) release by feedback inhibition (1-5). The molecular mechanisms underlying AcCho liberation, and in particular its modulation by muscarinic receptors, are not known.Protein phosphorylation and dephosphorylation is now recognized as a ubiquitous regulatory mechanism of enzymatic and cellular activities (for review, see ref. 6). Hence it is plausible that AcCho liberation, triggered in vivo and in vitro by an increased level of free Ca2+ in the nerve ending's cytoplasm (7-9), is accompanied by the phosphorylation of specific proteins. Krueger et al. (10) have shown that agents which increase Ca2+ transport into intact rat brain synaptosomes stimulate the incorporation of 32P, into synaptosomal proteins of apparent subunit molecular weights of 80,000 and 86,000. DeLorenzo (11) and Hershkowitz (12) used a preparation of rat brain synaptosomes and [y-32P]ATP and found Ca2+-dependent phosphorylation of specific proteins in the range of 60,000, 50,000, and 42,000 daltons. These findings show that Ca2+ can modulate protein phosphorylation of rat brain synaptosomes. Brain synaptosomes contain a mixture of nerve endings, and these endings use various neurotransmitters. Consequently, the phosphorylation observed in such preparations represents that of an ave...

show abstract

“…High-Mr MAPs have been shown to be particularly susceptible to a Ca 2 +-dependent protease in whole brain cytosol [9]. The physiological significance of the Ca2+-dependent proteolysis of MAPs and other polypeptides in synaptosomes is unclear since we could not demonstrate proteolysis in intact synaptosomes with conditions known to stimulate Ca 2+ influx [18]. The abSence of proteolysis can be explained on the basis of the low calcium sensitivity of the protease.…”

Section: Discussionmentioning

confidence: 78%

Evidence for the presence of high‐M_r microtubule‐associated proteins and their Ca²⁺‐dependent proteolysis in synaptosomal cytosol

Burgoyne

Cumming

1982

FEBS Letters

View full text Add to dashboard Cite

Calcium‐dependent proteolysis of several polypeptides from rat brain and synaptosomal cytosol was observed including proteolysis of polypeptides of M r 340 000 and 300 000. These latter polypeptides comigrated with high‐M r microtubule‐associated proteins of microtubule preparations from brain or synaptosomal cytosol. Calcium influx into intact synaptosomes due to depolarisation with high potassium or veratridine or treatment with the ionophore A23187 did not result in Ca2+‐dependent proteolysis of any polypeptides. This may be due to the low calcium sensitivity of the protease since no proteolysis of the M r 340 000 and 300 000 polypeptides was seen in synaptosomal cytosal at < 10 μM free Ca2+.

show abstract

Effects of potassium, veratridine, and scorpion venom on calcium accumulation and transmitter release by nerve terminals in vitro.

Abstract: somes: veratridine (7.5 x 106 to 7-5 x 10-5 M) and scorpion (Leirus quinquestriatus) venom (6-7 x 10-7 to 6-7 x 10-6 g/ml.

Cited by 551 publications

References 60 publications

THE SPONTANEOUS AND EVOKED RELEASE OF SPERMINE FROM RAT BRAIN in vitro

THE SPONTANEOUS AND EVOKED RELEASE OF SPERMINE FROM RAT BRAIN in vitro

Mechanism of acetylcholine release: possible involvement of presynaptic muscarinic receptors in regulation of acetylcholine release and protein phosphorylation.

Evidence for the presence of high‐M_r microtubule‐associated proteins and their Ca²⁺‐dependent proteolysis in synaptosomal cytosol

Contact Info

Product

Resources

About

Effects of potassium, veratridine, and scorpion venom on calcium accumulation and transmitter release by nerve terminals in vitro.

Abstract: somes: veratridine (7.5 x 106 to 7-5 x 10-5 M) and scorpion (Leirus quinquestriatus) venom (6-7 x 10-7 to 6-7 x 10-6 g/ml.

Cited by 551 publications

References 60 publications

THE SPONTANEOUS AND EVOKED RELEASE OF SPERMINE FROM RAT BRAIN in vitro

THE SPONTANEOUS AND EVOKED RELEASE OF SPERMINE FROM RAT BRAIN in vitro

Mechanism of acetylcholine release: possible involvement of presynaptic muscarinic receptors in regulation of acetylcholine release and protein phosphorylation.

Evidence for the presence of high‐Mr microtubule‐associated proteins and their Ca2+‐dependent proteolysis in synaptosomal cytosol

Contact Info

Product

Resources

About

Evidence for the presence of high‐M_r microtubule‐associated proteins and their Ca²⁺‐dependent proteolysis in synaptosomal cytosol