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 μg 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 μg of NT. In addition, peripheral (intravenous) administration of NT (100 μg/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 μg) 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.
ASJC Scopus subject areas
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience