Indoleamine-sensitive adenylate cyclase in rabbit retina: characterization and distribution.
Previous histological, electrophysiological, and biochemical reports have addressed the hypothesis that serotonin functions as a neurotransmitter in mammalian retinas. We have tested the effect on the levels of cyclic AMP of the application of exogenous serotonin, 5-methoxytryptamine, melatonin, and 5-methoxydimethyl-tryptamine to isolated, incubated rabbit retinas. All indoleamines tested significantly elevated intracellular levels of cyclic AMP in both light- and dark-adapted, incubated, intact retinas, provided a phosphodiesterase inhibitor was present. In homogenates of rabbit retina, all indoleamines tested also markedly increased adenylate cyclase activity over basal levels. Maximal activity was observed with 50 microM indoleamine; addition of GTP augmented this increase. The increase in enzyme activity persisted in the presence of known antagonists of dopamine and serotonin 5-HT2-receptors, but was blocked by the mixed 5-HT1, 5-HT2-antagonist lysergic acid diethylamide. The retinal locations of this response have also been identified using layer microdissection techniques on freeze-dried samples obtained from rabbit eyecups suprafused with indoleamine plus phosphodiesterase inhibitor. Cyclic AMP levels were measured in discrete retinal layers of both light- and dark-adapted suprafused eyecups, and increased levels were observed primarily in the inner and outer plexiform layers, which contain the synapses of the retinal neurons.
C
C
Blazynski
J A
JA
Ferrendelli
A I
AI
Cohen
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D008735:5-Methoxytryptamine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002415:Cats; D000242:Cyclic AMP / Q000032:analysis; D006152:Cyclic GMP / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D006801:Humans; D008550:Melatonin / Q000494:pharmacology; D008732:Methoxydimethyltryptamines / Q000494:pharmacology; D011817:Rabbits; D012160:Retina / Q000032:analysis / Q000187:drug effects / Q000201:enzymology*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014363:Tryptamines / Q000494:pharmacology*
D008732:Methoxydimethyltryptamines; D012702:Serotonin Antagonists; D014363:Tryptamines; D012701:Serotonin; D008735:5-Methoxytryptamine; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D006220:Haloperidol; D008550:Melatonin; D015056:1-Methyl-3-isobutylxanthine