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  • Title: Presynaptic adrenoceptors on the regulation of tyrosine hydroxylase activation by potassium.
    Author: Masana MI.
    Journal: Acta Physiol Pharmacol Latinoam; 1984; 34(3):245-51. PubMed ID: 6152372.
    Abstract:
    The role of the presynaptic alpha and beta-adrenoceptors on the regulation of tyrosine hydroxylase activity was studied in guinea pig atria depolarized with 50 mM K+. The presence of the beta-blocker propranolol (0.1 microM), alpha-blockers phentolamine (0.31 microM) or yohimbine (0.3 microM) or the alpha-agonist clonidine (0.1 microM) in the incubation medium did not affect tyrosine hydroxylase activation by 50 mM K+. On the contrary, the beta-agonist isoproterenol (0.012 microM) potentiated the activation produced by 50 mM K+, effect blocked by propranolol. Also the phosphodiesterase inhibitor, 1-methyl-3-isobutyl-xanthine (100 microM), facilitated tyrosine hydroxylase activation by potassium. Isoproterenol might exert its facilitatory effect through the stimulation of presynaptic beta-adrenoceptors, activation of adenyl cyclase and consequent increase of the intraneuronal concentration of cAMP. Noradrenaline synthesis in guinea pig atria depolarized by K+ seems to be unrelated to the stimulation of presynaptic adrenoceptors and also independent of the regulation of neurotransmitter release.
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