Effect of Bremazocine, a Kappa-Opioid Receptor Agonist, on Inositol Phosphate Formation in Isolated Iris-Ciliary Bodies

The goal of the current study was to examine the effect of the kappa-opioid agonist, bremazocine (BRE), on inositol phosphate (IP) formation in the rabbit iris-ciliary body (ICB). Concentrations of BRE (10 –7 to 10 –5 M) augmented levels of IP. Incubation of ICBs with BRE (10 –6 M) produced a time-dependent increase in IP levels that peaked at 60 s and declined to basal levels by 5 min. The increase in IP levels produced by BRE (10 –6 M) was inhibited by the kappa-opioid receptor antagonist, nor-binaltorphimine (nor-BNI, 10 –7 to 10 –5 M) and by activation of PKC with PDBu (10 –7 M). These results demonstrate that kappa-opioid receptor activation by BRE in the rabbit ICB is linked to IP production. Thus, opioid agonist-induced increases in IP activity could play a role in BRE-induced increases in atrial natriuretic peptide release and alterations in aqueous humor dynamics.