caa a22 4500 469078235 CHVBK 20180323132941.0 cr unu---uuuuu 170328e19920901xx s 000 0 eng 10.1007/BF00173544 doi (NATIONALLICENCE)springer-10.1007/BF00173544 Role of cyclic AMP in the release of noradrenaline from isolated rat atria [Elektronische Daten] Effect of pretreatment with clenbuterol [Marcelo Kazanietz, Maria Enero] Summary: The possible role of cyclic AMP (cAMP) on tritium overflow evoked by stimulation of the cardioaccelerant nerves was studied in rat atria preincubated with [3H]-noradrenaline. Addition of the activator of adenylate cyclase forskolin (1 µmol/l), or of the phosphodiesterase inhibitor 3-isobutyl-l-methylxanthine (IBMx, 100 µmol/l), did not affect both basal and evoked overflow. However, in the presence of the α2-adrenoceptor antagonist yohimbine (0.03 µmol/l) both forskolin and IBMx increased the stimulation-induced transmitter overflow by 49% and 141%, respectively (compared to yohimbine 0.03 µmol/l). Thus, in rat atria the cAMP-dependent facilitation of noradrenaline release is only present when the autoinhibition exerted by activation of prejunctional α2-adrenoceptors is blocked. Propranolol (0.1 µmol/l) that did not produce any effect on noradrenaline release markedly reduced the facilitatory response induced by forskolin in the presence of yohimbine. When rats were pretreated with the β2-adrenoceptor agonist clenbuterol (0.3 mg · kg−1, s. c., twice daily, 14 days), a treatment which desensitizes β-adrenoceptor-me-diated facilitation of noradrenaline release (Kazanietz and Enero 1989), the facilitatory effect of forskolin and IBMx in the presence of yohimbine was abolished. The results indicate that in rat atria the effect of forskolin and IBMx on noradrenaline release are only to be observed after blockade of presynaptic α2-adrenoceptor autoinhibition. β-adrenoceptor blockade or clenbuterol pre-treatment decreases the facilitatory response to forskolin and hence prejunctional β-adrenoceptor-mediated enhancement of noradrenaline release is linked to the stimulation of adenylate cyclase. Springer-Verlag, 1992 Rat atria nationallicence Noradrenaline release nationallicence Forskolin nationallicence Clenbuterol nationallicence Prejunctional adenylate cyclase nationallicence Kazanietz Marcelo Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, UBA., Instituto de Investigaciones Farmacológicas, CONICET, Junin 956 5, 1113, Buenos Aires, Argentina aut Enero Maria Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, UBA., Instituto de Investigaciones Farmacológicas, CONICET, Junin 956 5, 1113, Buenos Aires, Argentina aut Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/3(1992-09-01), 311-314 0028-1298 346:3<311 1992 346 210 https://doi.org/10.1007/BF00173544 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00173544 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kazanietz Marcelo Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, UBA., Instituto de Investigaciones Farmacológicas, CONICET, Junin 956 5, 1113, Buenos Aires, Argentina aut NATIONALLICENCE 700 1- Enero Maria Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, UBA., Instituto de Investigaciones Farmacológicas, CONICET, Junin 956 5, 1113, Buenos Aires, Argentina aut NATIONALLICENCE 773 0- Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/3(1992-09-01), 311-314 0028-1298 346:3<311 1992 346 210 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer