Enkephalin, neurotensin and somatostatin increase cAMP levels in the chicken retina.
OBJECTIVE
Enkephalin, neurotensin and somatostatin are released at high rates in the dark and at low rates in the light n the chicken retina. The present study examines the effects of these peptide transmitters on retinal cAMP METHODS: Chicken retinas were incubated in vitro with various drugs for 10min. Cyclic AMP was extracted with acidified ethanol and retinal levels of cAMP were measured using a radioassay kit.


CONCLUSIONS
These peptides increased cAMP levels in the chicken retina in vitro, which is surprising as their receptors are generally thought to be negatively coupled to adenylate cyclase. The paradoxical increase in retinal cAMP may be due to unique types of peptide receptors that are positively coupled to adenylate cyclase. A more plausible explanation is that these peptides act indirectly and change the rate of release of another transmitter, whose receptor is coupled to adenylate cyclase.
La Trobe University, Bendigo, Victoria, Australia. s.firth@bendigo.latrobe.edu.au
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Firth
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Boelen
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Morgan
D000818:Animals; D002645:Chickens; D000242:Cyclic AMP / Q000378:metabolism*; D004745:Enkephalins / Q000494:pharmacology*; D009496:Neurotensin / Q000494:pharmacology*; D009924:Organ Culture Techniques; D012160:Retina / Q000187:drug effects* / Q000378:metabolism; D013004:Somatostatin / Q000494:pharmacology*
D004745:Enkephalins; D009496:Neurotensin; D013004:Somatostatin; D000242:Cyclic AMP