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Intracellular calcium release mediated by noradrenaline and acetylcholine in mammalian pineal cells.

Abstract：

:The effects of noradrenergic and cholinergic receptor agonists on intracellular Ca2+ concentration ([Ca2+]i) in single dissociated rat pineal cells were investigated by microfluorimetric measurements in Fura-2 acetoxymethyl ester (Fura-2/AM) loaded cells. Noradrenaline (NA) evoked characteristic biphasic increments of intracellular Ca2+ consisting of one or more leading spikes followed by a plateau, resulting from the release of Ca2+ from intracellular stores and from the influx of Ca2+ from the external medium, respectively. This response was reproduced by the alpha 1-adrenoceptor agonist, phenylephrine (PE), in the presence of the beta-adrenoceptor antagonist, propranolol, and was abolished when NA or PE was applied in conjunction with the alpha 1-adrenoceptor antagonist, prazosin. The curve relating the peak amplitude of the Ca2+ increments to different PE concentrations (0.5-10 microM) showed a half-maximum response at 0.6 microM PE, and saturation at concentrations greater than 2 microM. Acetylcholine (ACh) also elicited transient Ca2+ increments consisting of an abrupt rise to a maximum value which decayed exponentially to the basal Ca2+ level. A half-maximum response was achieved at 59 microM ACh. The muscarinic cholinergic receptor agonist, carbachol (CCh), similarly activated Ca2+ increments while the muscarinic antagonist, atropine, abolished them. In the absence of extracellular Ca2+, repetitive stimuli with either alpha 1-adrenergic and muscarinic agonists produced a progressive decrement in the amplitude of the Ca2+ signals because of the depletion of intracellular stores. However, extinction of the response to muscarinic agonists did not preclude a response to adrenergic agonists, while the contrary was not true. These results suggest that these agonists liberate Ca2+ from two functionally distinct, caffeine-insensitive, Ca2+ intracellular stores.

journal_name

J Pineal Res

journal_title

Journal of pineal research

authors

Marín A,Ureña J,Tabares L

doi

10.1111/j.1600-079x.1996.tb00266.x

subject

Has Abstract

pub_date

1996-08-01 00:00:00

pages

15-28

issue

eissn

0742-3098

issn

1600-079X

journal_volume

pub_type

杂志文章

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Intracellular calcium release mediated by noradrenaline and acetylcholine in mammalian pineal cells.