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EFFECTS OF MAGNESIUM ON CONTRACTILE RESPONSES INDUCED BY ELECTRICAL TRANSMURAL STIMULATION AND NORADRENALINE IN RABBIT THORACIC AORTA
Author(s) -
FUJIWARA MOTOHATSU,
KITAGAWA HISATO,
KURAHASHI KAZUYOSHI
Publication year - 1978
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1978.tb07773.x
Subject(s) - magnesium , stimulation , medicine , chemistry , endocrinology , contraction (grammar) , vasodilation , thoracic aorta , vascular smooth muscle , muscle contraction , efflux , aorta , smooth muscle , biology , biochemistry , organic chemistry
1 In rabbit isolated thoracic aortae, effects of magnesium ions on the contraction and 3 H‐efflux in response to electrical transmural stimulation and on the contractile responses induced by noradrenaline and KCl were investigated. 2 Addition of magnesium (1.2, 3.6, 12.0 and 24.0 m m ) to the bathing solution inhibited the electrically induced contractions in a dose‐related manner; the inhibition was complete with a concentration of 24.0 m m . 3 The increase in 3 H‐efflux induced by electrical transmural stimulation was inhibited by the addition of magnesium to the superfusing fluid, but a complete block was not obtained even in high concentrations of magnesium. 4 Magnesium ions (1.2, 3.6, 12.0 and 24.0 m m ) inhibited the contractile responses induced by low concentrations of noradrenaline (2 × 10 8 m ) and KCl (2 × 10 −2 m ). However, the responses induced by higher concentrations of noradrenaline (5 × 10 −7 and 10 −5 m ) and KCl (3 and 4 × 10 −2 m ) were enhanced by low concentrations of magnesium. 5 Magnesium ions affect both presynaptic and effector sites in rabbit thoracic aortae but in a different manner; magnesium manifests only an inhibitory effect on noradrenaline release from the adrenergic nerves, but dual effects on reactivity of vascular smooth muscle, depending on concentrations of magnesium and stimulants; it is suggested that the change in vascular reactivity is more important than the reduction in transmitter release when magnesium inhibits the response to nerve stimulation.