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.