The role of calcium in the effects of noradrenaline and phenoxybenzamine on adrenergic transmitter release from atria: no support for negative feedback of release

British Journal of Pharmacology
S Kalsner

Abstract

1 The relation of calcium ion influx into nerve terminals to presynaptic adrenoceptor function and the possible masking, by desensitization due to intraneuronal calcium accumulation, of the effects of adrenoceptor agonists and antagonists on presynaptic alpha-adrenoceptors was investigated in guinea-pig atria previously incubated with [(3)H]-noradrenaline.2 Atria were stimulated with 100 pulses at various frequencies (1 to 15 Hz) in standard (2.3 mm), low (0.26 mm) and high (6.9 mm) calcium-Krebs solution in the absence and then the presence first of noradrenaline and subsequently phenoxybenzamine.3 The per pulse overflow of tritium was directly related to the calcium concentration of the Krebs solution, being much reduced and substantially increased in 0.26 and 6.9 mm calcium-Krebs solutions respectively.4 Noradrenaline inhibited the overflow of tritium in low calcium-Krebs solution, to a relatively constant extent, independently of frequency. In addition, the agonist had a greater maximal inhibitory effect in standard than in reduced calcium-Krebs. The catecholamine was as effective an inhibitor of overflow at the lowest and highest frequencies in high as it was in standard calcium-Krebs solution. Phenoxybenzamine invariably ...Continue Reading

References

Jan 1, 1977·Reviews of Physiology, Biochemistry and Pharmacology·K Starke
Apr 28, 1978·Annals of the New York Academy of Sciences·M P BlausteinN K Kendrick
Oct 1, 1979·Canadian Journal of Physiology and Pharmacology·C C Chan, S Kalsner
Oct 1, 1977·Physiological Reviews·T C Westfall
Jul 1, 1979·Canadian Journal of Physiology and Pharmacology·S Kalsner
Apr 1, 1980·The Journal of Pharmacy and Pharmacology·S KalsnerR E Dobson

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Citations

Mar 1, 1984·Naunyn-Schmiedeberg's Archives of Pharmacology·N Limberger, K Starke
Dec 1, 1985·British Journal of Clinical Pharmacology·M J BrownD C Brown
Jan 1, 1990·Annals of the New York Academy of Sciences·T C Westfall
Dec 1, 1981·Journal of Autonomic Pharmacology·M W McCullochI Sutton

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