Encyclopedia of Health and Medicine

nociceptor 381
the dendrites of neurons that detect pain and initiate
transmission of pain signals to the CENTRAL
NERVOUS SYSTEM. Neurogenic pain often follows an
injury (traumatic or surgical) for which pain is a
reasonable symptom. However, when the injury
heals, the nociceptors can remain hypersensitive
to stimuli, particularly touch and temperature,
which they perceive as painful, and the nociceptors
continue to initiate pain signals. Neurogenic
pain often accompanies degenerative neurologic
conditions such as MULTIPLE SCLEROSIS and pain syndromes
such as trigeminal NEURALGIA and COMPLEX
REGIONAL PAIN SYNDROME.
The sensation of neurogenic pain is characteristically
that of a persistent tingling, burning, or
“pins and needles” feeling. Some people also feel
sharp stabs of pain. The diagnostic path typically
includes evaluation of other potential causes for
the pain in the context of any history of a musculoskeletal
injury or neurologic condition. Diagnosis
is often clinical (based on symptoms) after the
doctor has assessed or ruled out possible conditions
that could account for the symptoms.
MEDICATIONS TO TREAT NEUROGENIC PAIN
amitriptyline
baclofen
carbamazepine
dantrolene
desipramine
fluoxetine
gabapentin
paroxetine
phenytoin
sertraline
tizanidine
valproic acid
Because neurogenic pain results from NERVOUS
SYSTEM dysfunction, conventional ANALGESIC MED-
ICATIONS such as NONSTEROIDAL ANTI-INFLAMMATORY
DRUGS (NSAIDS) and narcotics are not especially
effective for providing pain relief. Low-DOSE tricyclic
ANTIDEPRESSANT MEDICATIONS and antiseizure
medications often do provide relief, apparently
through their influence on BRAIN neurotransmitters.
Selective serotonin reuptake inhibitor (SSRI)
antidepressants are also effective in some people.
These medications may cause potentially serious
side effects, especially antiseizure medications.
Treatment may control pain until the underlying
condition improves or may be a long-term therapeutic
process, depending on the cause of the dysfunction.
See also NEURON; NEUROTRANSMITTER; NOCICEPTOR;
PSYCHOGENIC PAIN.
nociceptor A specialized molecule on the dendrite
of a sensory NEURON that interprets stimuli as
PAIN and activates NERVE fibers (C fibers and A-
delta fibers) to send pain signals to the CENTRAL
NERVOUS SYSTEM. Nociceptors activate the withdrawal
REFLEX—the sudden, involuntary movement
to get away from the stimulus such as
jerking one’s hand from a hot surface. Sensory
neurons often have extensive networks of dendrites,
the branchlike fibers that extend from the
nerve body to draw input into the neuron. Nociceptors
pepper these dendrites, serving as one of
the body’s most primal warning mechanisms of
danger from physical harm. They respond to sensations
of heat, cold, sharp, and pressure.
TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION
(TENS), a pain relief method, uses mild electrical
current to stimulate nociceptors. Researchers
believe this either restores the neuron’s normal
perceptions of stimuli or overloads the neuron so
that it cannot transmit pain signals. Doctors
believe counterirritants such as capsaicin topical
ointment work in a similar fashion. Some Western
researchers believe ACUPUNCTURE’s effectiveness for
pain relief comes from its ability to stimulate or
block nociceptor function; Western doctors often
combine electrical stimulation with acupuncture
to intensify this effect.
For further discussion of nociceptors, please see
the overview section “Pain and Pain Management.”
See also ALTERNATIVE METHODS FOR PAIN RELIEF;
ANALGESIC MEDICATIONS; DERMATOME; PROPRIOCEPTION;
SPINAL NERVES; TRADITIONAL CHINESE MEDICINE (TCM).