The Journal of Neuroscience, August 15, 1998, 18(16):6480-6491
Nociceptor Hyper-Responsiveness during Vincristine-Induced
Painful Peripheral Neuropathy in the Rat
Kimberly D.
Tanner,
David B.
Reichling, and
Jon D.
Levine
Departments of Medicine, Anatomy, and Oral and Maxillofacial
Surgery, Division of Rheumatology, and Program in Neuroscience,
University of California, San Francisco, California 94143-0452
Neuropathic pain accompanies peripheral nerve injury after a wide
variety of insults including metabolic disorders, traumatic nerve
injury, and neurotoxic drugs. Chemotherapy-induced neuropathic pain,
caused by drugs such as vincristine and taxol, occurs in cancer
patients who receive these drugs as antineoplastic agents. Although a
variety of remediations have been attempted, the absence of knowledge
concerning mechanisms of chemotherapy-induced neuropathic pain has
hindered the development of treatment strategies. Vincristine, a widely
used chemotherapeutic agent, produces painful peripheral neuropathy in
humans and mechanical hyperalgesia in rats. To test the hypothesis that
alterations in C-fiber nociceptor function occur during
vincristine-induced painful peripheral neuropathy, we performed
in vivo extracellular recordings of single neurons from
the saphenous nerve of vincristine-treated rats. Forty-one percent of
C-fiber nociceptors were significantly hyper-responsive to
suprathreshold mechanical stimulation. As a population, these mechanically hyper-responsive nociceptors also had significantly greater responses to suprathreshold heat stimulation; however, heat
hyper-responsiveness was found only in a subset of these nociceptors
and was never detected in the absence of mechanical hyper-responsiveness. In addition, mean conduction velocities of
A-fibers and C-fibers in vincristine-treated rats were
significantly slowed. Mean heat and mechanical activation thresholds of
C-fiber nociceptors, their distribution among subclasses, and the
percentage of spontaneously active neurons in vincristine-treated rats
were not statistically different from controls. Vincristine does not, therefore, cause generalized impairment of C-fiber nociceptor function
but rather specifically interferes with mechanisms underlying responsiveness to suprathreshold stimuli. Furthermore,
vincristine-induced nociceptor hyper-responsiveness may involve
alterations specifically in mechanotransduction in some nociceptors and
alterations in general cellular adaptation mechanisms in others.
Key words:
C-fiber; primary afferent nociceptor; neuropathic pain; peripheral neuropathy; vincristine; mechanotransduction
Copyright © 1998 Society for Neuroscience 0270-6474/98/18166480-12$05.00/0