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Chapter 8. Analgesic Adjuvants in the Peripheral Nervous System

Which of the following is not a chemical mediator of tissue damage/inflammation causing nociceptive pain in peripheral nerves?

A. Bradykinin

B. Somatostatin

C. Serotonin

D. Glutamate

B is correct. Somatostatine is not a chemical mediator. Chemical mediators in a wide array are produced in the peripheral nervous system and have both excitatory and inhibitory influences on peripheral sensory nerve transmission. Figure 8–1 includes a list of the mediators released by tissue injury and inflammation and a variety of agents acting on neuroreceptors. Bradykinin, serotonin, and glutamate have an excitatory influence while somatostatin has an inhibitory influence.

Figure 8–1

Excitatory and inhibitory influences on peripheral nerve activity by mediators released by tissue injury and inflammation and by a variety of agents acting on neuroreceptors. AMPA = α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid; KA = kainic acid; NMDA = N-methyl-D-aspartate; NK = neurokinin; TrkA = Tropomyosin receptor kinase A.

The suppression of which currents cause attenuation of substance P release?

A. Mg2+

B. PO43-

C. K+

D. Ca2+ and Na+

D is correct. Opioid receptors and neuropeptides (eg, substance P) are synthesized in the dorsal root ganglion and transported along intra-axonal microtubules into central and peripheral processes of the primary afferent neuron. At the terminals, opioid receptors are incorporated into the neuronal membrane and become functional receptors. On activation by exogenous or endogenous opioids, opioid receptors couple to inhibitory G proteins. This leads to direct or indirect suppression of Ca2+ or Na+ currents and subsequent attenuation of substance P release.

The perineural administration of which opioid in conjunction with local anesthetics have demonstrated analgesic efficacy and increase in duration of analgesia?

A. Buprenorphine

B. Morphine

C. Fentanyl

D. Sufentanil

A is correct. The two opioid agonists that have demonstrated analgesic efficacy when administered perineuronally are buprenorphine and tramadol. Buprenorphine is a partial μ-receptor agonist with a very high receptor affinity compared with fentanyl (24-fold) or morphine (50-fold). In addition, it has intermediate lipid solubility, which allows it to cross the neural membrane.1,2 Candido and colleagues3 added 0.3 mg buprenorphine ...

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