17. Which of the following description about spinal cord plasticity and pain is incorrect? (A) Some spinal nociceptive neurons receive convergent input from high- and low- threshold sensory fibers thus called wide–dynamic range neurons (B) Glutamate is the major fast excitatory neurotransmitter in all nociceptive afferent nerve fibers. Glutamate can bind to three types of ionotropic glutamate receptors and to G protein–coupled metabotropic glutamate receptors to modify neuroexcitability. (C) Hyperalgesia and allodynia can even be induced in humans in the absence of any sensory stimuli, such as during prolonged application of opioids or on abrupt withdrawal of opioids.. (D) Spinal nociception is under powerful control from descending inhibitory and facilitatory pathways. Under normal conditions, descending facilitation appears to prevail over inhibitory pathway.