Neomycin blocks substance P-induced calcium entry in cultured rat spinal cord neurons

Substance P (SP) plays an important role in sensitization of spinal cord neurons. In this study, we investigated SP-induced calcium activities in cultured rat spinal cord neurons with confocal laser scanning microscopy. Our results showed that SP increased [Ca(2+)](i) by calcium entry rather than release from intracellular calcium stores. Neomycin (100 microM), an antagonist of phosphatidylinositol 4,5-bisphosphate (PIP(2)), blocked SP-induced calcium entry. Ca(2+)-free medium induced capacitative entry, which was significantly potentiated by SP. As activation of SP receptor (NK-1) leads to production of inositol 1,4,5-trisphosphate (IP(3)) by PIP(2) turnover, the results indicates that SP-induced calcium entry and SP-potentiated capacitative calcium entry might be mediated or regulated by IP(3)/diacylglycerol (DG) pathway.