A 34-year-old man was brought to the emergency room after a serious car accident.
He begun to experience sever pain throughout the body. Which of the following triplets
of neurotransmitters most likely acted to decrease pain signaling in this patient?
A. Norepinephrine, GABA, glutamate B. Glutamate, norepinephrine, opioid peptides C. Histamine, acetylcholine, GABA D. Histamine, acetylcholine, opioid peptides E. Glutamate, GABA, serotonin F. Opioid peptides, norepinephrine, serotonin
Opioid peptides, norepinephrine, serotonin-answer: f(katzung, pp 501, golan, pp 233)opioid peptides, serotonin and norepinephrine are the three major neurotransmitters that act inthe cns to decrease pain signaling and producing analgesia. endogenous opioids arereleased at several cns sites in response to noxious stimuli, including the spinal cord, thethalamus and the cortex. endogenous opioids can also modulate pain transmission indirectly,by activating the following pathways that descend from the brainstem to the dorsal horn:a) a noradrenergic pathway from the locus ceruleus. norepinephrine, released from theseprojections in the spinal cord, activates alpha-2 receptors (the primary receptors fornorepinephrine in the cns) located on nociceptive neurons of the dorsal horn. this activationcauses hyperpolarization of the neuron so inhibiting nociceptive transmission.b) a serotonergic pathway from the raphe nuclei. serotonin, released from these projections inthe spinal cord, activates serotonergic receptors located on nociceptive neurons of the dorsalhorn. this activation causes hyperpolarization of the neuron so inhibiting nociceptivetransmissiona, b, c, d, e) (see explanation above)