Cholecystokinin causes contraction of the pupillary sphincter in monkeys but not in cats, rabbits, rats and guinea-pigs: antagonism by lorglumide.
The effects of intracameral injections of cholecystokinin (CCK) on the pupil size were determined in monkeys, cats, rabbits, rats and guinea-pigs. In animals under muscarinic cholinergic blockade, CCK caused miosis in monkeys but not in the other species investigated. In monkeys CCK-8 was more potent than CCK-33, which was, however, much more potent than non-sulphated CCK-8. These observations indicate that peripheral type A receptors mediated the miotic response. The effect of CCK-8 was not appreciably influenced by pretreatment with indomethacin, 3 mg kg-1 body wt, indicating that prostaglandins were not involved in the response. Nerve blockade with 0.9 micrograms tetrodotoxin intracamerally had no clear effect on the dose-response relationship for CCK-8. The effect of the peptide thus seems to be directly on receptors on the pupillary sphincter muscle. Pretreatment with lorglumide caused a dose-dependent rightward shift of the dose-response curve, indicating competitive antagonism. The results indicate that in monkeys, but not in rabbit, cats, rats and guinea-pigs, CCK is a potent miotic with a direct effect on the pupillary sphincter mediated by type A CCK receptors on the muscle.
Bill
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Department of Physiology and Medical Biophysics, University of Uppsala, Sweden.
Andersson
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Almegård
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B
D000818:Animals; D002415:Cats; D002766:Cholecystokinin / Q000494:pharmacology*; D005123:Eye / Q000033:anatomy & histology / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D007213:Indomethacin / Q000494:pharmacology; D008251:Macaca / Q000502:physiology*; D008252:Macaca fascicularis / Q000502:physiology*; D008297:Male; D015877:Miosis / Q000139:chemically induced; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D009799:Ocular Physiological Phenomena; D011377:Proglumide / Q000031:analogs & derivatives / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011949:Receptors, Cholecystokinin / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology
D011949:Receptors, Cholecystokinin; D013779:Tetrodotoxin; D002766:Cholecystokinin; D011377:Proglumide; C048181:lorglumide; D007213:Indomethacin