title: Norepinephrine acts as D1-dopaminergic agonist in the embryonic avian retina: late expression of beta1-adrenergic receptor shifts norepinephrine specificity in the adult tissue.
abstract: Dopamine is the main catecholamine found in the chick retina whereas norepinephrine is only found in trace amounts. We compared the effectiveness of dopamine and norepinephrine in promoting cyclic AMP accumulation in retinas at embryonic day 13 (E13) and from post-hatched chicken (P15). Dopamine (EC(50)=10microM) and norepinephrine (EC(50)=30microM), but not the beta(1)-adrenergic agonist isoproterenol, stimulated over seven-fold the production of cyclic AMP in E13 retina. The cyclic AMP accumulation induced by both catecholamines in embryonic tissue was entirely blocked by 2microM SCH23390, a D(1) receptor antagonist, but not by alprenolol (beta-adrenoceptor antagonist). In P15 retinas, 100microM isoproterenol stimulated five-fold the accumulation of cAMP. This effect was blocked by propanolol (10microM), but not by 2microM SCH23390. Embryonic and adult retina display beta(1) adrenergic receptor mRNA as detected by RT-PCR, but the beta(1) adrenergic receptor protein was detected only in post-hatched tissue. We conclude that norepinephrine cross-reacts with D(1) dopaminergic receptor with affinity similar to that of dopamine in the embryonic retina. In the mature retina, however, D(1) receptors become restricted to activation by dopamine. Moreover, as opposed to the embryonic tissue, norepinephrine seems to stimulate cAMP accumulation via beta(1)-like adrenergic receptors in the mature tissue.
authors.affiliation: Lab. Neurochemistry, Program in Neurobiology IBCCF, UFRJ, Rio de Janeiro, Brazil.
authors.forename: Regina Celia Cussa
authors.initials: RC
authors.lastname: Kubrusly
authors.forename: Ana Lúcia Marques
authors.initials: AL
authors.lastname: Ventura
authors.forename: Ricardo Augusto
authors.initials: RA
authors.lastname: de Melo Reis
authors.forename: Gracinda Conceição Fernandes
authors.initials: GC
authors.lastname: Serra
authors.forename: Edna Nanami
authors.initials: EN
authors.lastname: Yamasaki
authors.forename: Patrícia Franca
authors.initials: PF
authors.lastname: Gardino
authors.forename: Maria Christina Fialho
authors.initials: MC
authors.lastname: de Mello
authors.forename: Fernando Garcia
authors.initials: FG
authors.lastname: de Mello
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D018491:Dopamine Agonists / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology*; D011869:Radioligand Assay; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism*; D017447:Receptors, Dopamine D1 / Q000819:agonists*; D012160:Retina / Q000166:cytology / Q000187:drug effects* / Q000196:embryology
chemical_list: D001552:Benzazepines; D018491:Dopamine Agonists; D018342:Receptors, Adrenergic, beta-1; D017447:Receptors, Dopamine D1; D009638:Norepinephrine