Adenosine A2 receptor-mediated stimulation of cyclic AMP in cultured chicken pineal cells

Authors

  • Jack Falcón,

    Corresponding author
    1. Laboratoire de Neurobiologie et Neuroendocri-nologie Cellulaires, Departement des Neurosciences de I'URA CNRS No. 1869, UFR Sciences, Poitiers, France
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  • Gilles Van Camp,

    1. Laboratoire de Neurobiologie et Neuroendocri-nologie Cellulaires, Departement des Neurosciences de I'URA CNRS No. 1869, UFR Sciences, Poitiers, France
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  • Jean Pierre Collin

    1. Laboratoire de Neurobiologie et Neuroendocri-nologie Cellulaires, Departement des Neurosciences de I'URA CNRS No. 1869, UFR Sciences, Poitiers, France
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Address reprint requests to Dr. J. Falcon, Laboratoire de Neurobiologie et Neuroendocrinologie Cellulaires, Departement des Neurosciences de I'URA CNRS No. 1869, UFR Sciences, 40 Avenue du Recteur Pineau, 86022 Poitiers cedex, France.

Abstract

Abstract: The pineal gland of vertebrates produces the time-keeping hormone melatonin in a rhythmic manner. Regulation of melatonin production is a multifactorial process. In the chicken, light, perceived through the skull, and norepinephrine, acting through α2-adrenergic receptors, synergistically inhibit day time melatonin production. In addition, adenosine exerts autocrine/paracrine modulatory effects on melatonin secretion. In an attempt to elucidate how these effects of adenosine are mediated, chicken pineal cells were cultured, in the dark during day time, in the presence of different analogs of adenosine. When the adenosine transmembranous carrier was inhibited, chloroadenosine stimulated cyclic AMP (cAMP) accumulation in a time- and dose-dependent manner. The effects were antagonized by 8-phenyltheophylline, an antagonist at the A1/A2 adenosine receptors. A dose-dependent stimulation of cAMP accumulation was also obtained with other adenosine agonists, with the following order of potency: N-ethylcarboxamidoadenosine > cyclopentyladenosine > R-phenyl-isopropylade-nosine. The stimulatory effect of the latter compound was still observed when basal cAMP levels were increased in the presence of forskolin. Under our experimental conditions no inhibition of cAMP content was observed. Our results are consistent with the idea that stimulation of melatonin secretion by adenosine analogs is mediated through A2 receptors.

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