Spinorphin

Spinorphin is a heptapeptide, and is a potent enkephalin-degrading enzymes inhibitor.Spinorphin inhibited cytoplasmic Ca (2+) ([Ca (2+) ]i) transients, evoked by depolarization and capsaicin selectively in medium and small cultured rat DRG neurons. Spinorphin (10-300 M) inhibited the Ca (2+) signals in concentration dependant manner in small- and medium diameter DRG neurons. Capsaicin produced [Ca (2+) ]i responses only in small- and medium-sized DRG neurons, and pre-treatment with spinorphin significantly attenuated these [Ca (2+) ]i responses. Spinorphin significantly inhibited the functions of polymorphonuclear neutrophils (PMNs) by suppressing the binding of fMLF to its receptor on PMNs. Further, this inhibitor suppressed the carrageenan-induced accumulation of PMN in mouse air pouches after intravenous administration. These results indicate that spinorphin may be an endogenous anti-inflammatory regulator. The possible role of spinorphin and its analog as regulators in pain and inflammation will be discussed.