Final answer:
Descending pain pathways in the spinal cord synapse on inhibitory interneurons in the dorsal horn through a process known as disinhibition, where substances like endomorphins moderate the perception of pain.
Step-by-step explanation:
The student's question pertains to the mechanism by which descending pain pathways affect the activity of interneurons in the dorsal horn of the spinal cord. In the context of descending pain modulation, these pathways synapse on an inhibitory interneuron.
The neurotransmitter released in this disynaptic connection reduces the inhibition of the target neuron, allowing for a decreased perception of pain, a concept known as disinhibition. Specifically, in the dorsal horn of the spinal cord, where sensory information from the dorsal (posterior) root ganglion is processed, substances like endomorphins may interact with the nociceptive (pain) system to modulate pain.