Opioid receptors are highly concentrated in which region of the CNS and produce pain relief through the release of endogenous opioids?

Question

A) The enkephalins
B) Primary afferent neurons
C) Thalamus
D) Periaqueductal gray (PAG) region

Answer 1

Ans: D
Feedback:
A major advance in understanding pain was the discovery of neuroanatomic pathways that arise in the midbrain and brain stem, descend to the spinal cord, and modulate ascending pain impulses. One such pathway begins in an area of the midbrain called the periaqueductal gray (PAG) region. Opioid receptors are highly concentrated in this region of the CNS and produce analgesia (pain relief) through the release of endogenous opioids. Three families of opioid peptides have been identified—the enkephalins, endorphins, and dynorphins. Although they appear to function as neurotransmitters, their full significance in pain control and other physiologic functions is not completely understood. There is evidence that opioid receptors and endogenously synthesized opioid peptides are found on the peripheral processes of primary afferent neurons and in many regions of the CNS.