Premium
THE PART PLAYED BY CALCIUM IN DETERMINING THE RESPONSE TO STIMULATION OF SYMPATHETIC POSTGANGLIONIC FIBRES
Author(s) -
BURN J. H.,
GIBBONS W. R.
Publication year - 1964
Publication title -
british journal of pharmacology and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0366-0826
DOI - 10.1111/j.1476-5381.1964.tb01708.x
Subject(s) - calcium , acetylcholine , chemistry , endocrinology , stimulation , ileum , medicine , nicotine , adrenal medulla , catecholamine , biochemistry , biology
The inhibition of the pendular movements in a loop of rabbit ileum caused by stimulating the periarterial nerves in the mesentery depends on the calcium concentration in the bathing fluid. The inhibition is small when the concentration is low, and increases as the concentration rises. In the lower ranges of calcium concentration there is rarely any change in the response to noradrenaline, so that the increase in inhibition is due to an increase in the amount of noradrenaline released. The effect of calcium is antagonized by magnesium. In the presence of hyoscine, nicotine inhibits the ileum, and this inhibition also depends on the concentration of calcium. Acetylcholine can sometimes be shown to cause inhibition, and again this inhibition depends on the concentration of calcium. These and other experiments show a close similarity between the release of catechol amines from the adrenal medulla by acetylcholine and the release of noradrenaline from the postganglionic fibre by stimulation or by nicotine. In both instances the calcium concentration plays a decisive part.