Activation of Neurons in the ___ Ultimately Results in ___

Activation of neurons in the ___ ultimately results in ___ in the ___.

A) periacqueductal gray,depletion of substance P,periacqueductal gray
B) spinal cord,inhibition of opiate release,periacqueductal gray
C) periacqueductal gray,inhibition of substance P release,spinal cord
D) periacqueductal gray,inhibition of substance P release,periacqueductal gray