Norepinephrine acts as D1-dopaminergic agonist in the embryonic avian retina: late expression of beta1-adrenergic receptor shifts norepinephrine specificity in the adult tissue.
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.
Kubrusly
Regina Celia Cussa
RC
Lab. Neurochemistry, Program in Neurobiology IBCCF, UFRJ, Rio de Janeiro, Brazil.
Ventura
Ana Lúcia Marques
AL
de Melo Reis
Ricardo Augusto
RA
Serra
Gracinda Conceição Fernandes
GC
Yamasaki
Edna Nanami
EN
Gardino
Patrícia Franca
PF
de Mello
Maria Christina Fialho
MC
de Mello
Fernando Garcia
FG
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
D001552:Benzazepines; D018491:Dopamine Agonists; D018342:Receptors, Adrenergic, beta-1; D017447:Receptors, Dopamine D1; D009638:Norepinephrine