ENKEPHALIN, NEUROTENSIN AND SOMATOSTATIN INCREASE CAMP LEVELS IN THE CHICKEN RETINA

Purpose: Enkephalin, neurotensin and somatostatin are released at high rates in the dark and at low rates in the light in 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 10 min. Cyclic AMP was extracted with acidified eth anol and retinal levels of cAMP were measured using a radioassay kit. Results/Conclusions: These pep-tides increased cAMP levels in the chic ken retina in vitro, which is surprising as their receptors are genera lly thought to be negatively coupled to adenylate cyclase.The paradoxi cal increase in retinal cAMP may be due to unique types of peptide rec eptors that are positively coupled to adenylate cyclase. A more plausi ble explanation is that these peptides act indirectly and change the r ate of release of another transmitter, whose receptor is coupled to ad enylate cyclase.