title: Noradrenaline action on cat retinal ganglion cells is mediated by dopamine (D2) receptors.
abstract: Effects of iontophoretically applied noradrenaline, dopamine and their receptor antagonists on the retinal ganglion cells, were studied in optically intact eyes of barbiturate-anaesthetized cats. Noradrenaline inhibited visually evoked and spontaneous firing of all classes of retinal ganglion cells: the effect being greater on ON- than on OFF-cells and slightly more potent than dopamine on a given cell. All alpha- and beta-adrenoreceptor blockers tested tended to change spikes, but were generally ineffective in blocking the noradrenaline-induced inhibition, when not affecting spikes. The noradrenaline-induced inhibition was, however, effectively blocked by dopamine D2-receptor antagonists. The alpha- and beta-adrenoreceptor antagonists applied alone had no effect, suggesting the absence of endogenous noradrenergic antagonism, although alpha-type adrenergic antagonism was suggestive on a very small number of cells. These results suggest that: (1) noradrenaline action on cat retinal ganglion cells is mediated via dopamine D2-receptors; (2) noradrenaline is not generally released on them, except there may be physiologically active alpha-receptors on a few cells; and (3) many of the adrenoreceptor blockers affect membrane properties of the retinal ganglion cells, in a similar manner to local anaesthetics.
authors.affiliation: Vision Research Unit of Sherrington School, Rayne Institute, St. Thomas' Hospital, London, U.K.
authors.forename: J
authors.initials: J
authors.lastname: Robbins
authors.forename: K
authors.initials: K
authors.lastname: Wakakuwa
authors.forename: H
authors.initials: H
authors.lastname: Ikeda
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D007478:Iontophoresis; D009638:Norepinephrine / Q000494:pharmacology*; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D017448:Receptors, Dopamine D2; D012160:Retina / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D013565:Sympatholytics / Q000494:pharmacology
chemical_list: D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D013565:Sympatholytics; D009638:Norepinephrine