title: Intracameral administration of neurotensin induces miosis in the rabbit.
abstract: The present investigation was designed to evaluate the effect of selected peptides on pupillary diameter and intraocular pressure (IOP) in rabbits. Intracameral (IC) administration of neurotensin (NT) in doses of 5-100 micrograms produced a significant, long lasting and dose-dependent decrease in pupillary diameter without affecting IOP. NT-induced miosis appears to be relatively specific because a variety of peptides including Gn-RH, somatostatin, met-enkephalin, bombesin, leu-enkephalin or NT1-6, (a biologically inactive N-terminal fragment of NT), produced no effect on pupillary diameter; only substance P produced miosis similar to NT when tested in a dose equimolar to 30 micrograms of NT. In addition, peripheral (intravenous) administration of NT (100 micrograms/kg) was equally ineffective. Inhibition of prostaglandin synthesis with indomethacin, did not prevent subsequent NT-induced miosis. Finally, IC administration of an effective dose of NT (30 micrograms) did not alter the protein concentration in the aqueous humor. These results indicate that NT-induced miosis is not mediated by endogenous prostaglandins and that this effect of NT does not appear to involve disruption of the blood-aqueous barrier, suggesting that NT may play a role in regulation of pupillary diameter.
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004743:Enkephalin, Leucine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D009496:Neurotensin / Q000008:administration & dosage / Q000494:pharmacology*; D011817:Rabbits; D012025:Reflex, Pupillary / Q000187:drug effects*; D013004:Somatostatin / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology
chemical_list: D013373:Substance P; D007987:Gonadotropin-Releasing Hormone; D009496:Neurotensin; D013004:Somatostatin; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine