The nervous system’s detection and processing of painful stimuli — what turns tissue damage into the experience of pain.Substance P is a key nociceptive neurotransmitter via NK1 receptor activation on pain-processing neurons in the dorsal horn of the spinal cord. Ziconotide (Prialt), derived from cone snail venom, blocks N-type calcium channels in spinal pain-transmission neurons — the most potent analgesic peptide drug approved for intrathecal use in refractory chronic pain (including cancer pain and failed back surgery syndrome). Its approval is specifically for intrathecal (spinal) delivery, not systemic.