Substance P in the cerebrospinal fluid-contacting nucleus contributes to morphine physical dependence in rats

▶ SP in CSF-CN was activated by chronic morphine treatment. ▶ (D-Pro2, D-Phe7, D-Trp9)-SP reduced naloxne precipitation withdrawal signs. ▶ Pain threshold was up-regulated by (D-Pro2, D-Phe7, D-Trp9)-SP. ▶ SP in CSF-CN was reduced by (D-Pro2, D-Phe7, D-Trp9)-SP. ▶ SP in CSF-CN is up-regulated by naloxone injection on morphine withdrawal.