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The effect of endothelin-1 (ET-1) was investigated in the isolated spinal cord of the newborn rat. Bath-applied ET-1 produced a depolarization of a lumbar ventral root, which was suppressed by nicardipine or a substance P antagonist (spantide). In addition, the slow ventral root depolarization from L4 segment evoked by electrical stimulation of the contralateral sciatic nerve was also suppressed by spantide or nicardipine. However, nicardipine did not affect the ventral root depolarization induced by substance P, itself. These results indicate that the dihydropyridine-sensitive Ca2+ channels are associated with substance P release and that the effect of endothelin is probably mediated by substance P.
Yoshizawa et al. (1989) studied this question.