One Way That Nociception (The Sensation of Pain) Is Modulated

Essay

One way that nociception (the sensation of pain) is modulated is by presynaptic inhibition of transmitter release from the nociceptive sensory neuron onto its postsynaptic target that takes information to the central nervous system (Figure Q3-48). Endogenous opioids (endorphins) are released onto the presynaptic terminal of the nociceptive sensory neuron. Figure Q3-48
A. If endorphins eventually result in an increased probability of Ca²⁺ channel closure, what will happen to the amount of glutamate release from the sensory neuron? Increase or decrease?
B. What would happen to Ca²⁺ channels if a G protein were activated in the absence of endorphin release?
C. Would endorphin result in synaptic facilitation or depression?