DOI
https://doi.org/10.25772/77fp-sb65
Author ORCID Identifier
https://orcid.org/0000-0003-3828-1605
Defense Date
1991
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Physiology
First Advisor
David J. Mayer, Ph.D.
Second Advisor
Donald D. Price, Ph.D.
Third Advisor
Barry E. Stein, Ph.D.
Fourth Advisor
John G. McHaffie, Ph.D.
Fifth Advisor
Stephen J. Goldberg, Ph.D.
Sixth Advisor
Margaret C. Boadle-Biber, Ph.D.
Abstract
In order to better characterize spatial and temporal mechanisms of nociceptive processing in the central nervous system (CNS), the responses of rat spinal cord neuron populations to prolonged painful stimuli were examined. Metabolic mapping studies revealed that prolonged nociceptive thermal stimuli produced extensive activation in the deep dorsal horn, but minimal activation in the superficial dorsal horn. Electrophysiological investigations of neurons within these regions revealed that the responses of wide dynamic range (WDR) neurons, the predominate nociceptive neuron in the deep dorsal horn, did not habituate substantially to prolonged nociceptive stimuli. In contrast, the responses of nociceptive specific neurons, the predominate nociceptive neuron in the superficial dorsal horn, exhibited significant habituation to prolonged nociceptive stimulation. Psychophysical assessments in humans revealed that, like the responses of WDR neurons, neither sensory-discriminitive nor affective responses adapted to prolonged painful stimuli. Thus, WDR neurons are sufficient to encode sensory-discriminitive features of nociceptive stimuli and to produce affective responses to pain. Discharge frequencies of WDR neurons alone do not provide sufficient information to encode the distinction between innocuous and nociceptive stimuli, since both types of stimuli elicit excitatory activity from WDR neurons. However, metabolic mapping of the rat spinal cord indicated that nociceptive (45°-49°C) temperatures activated regions extending from segments L1-L5. In contrast, brushing evoked metabolic activity was confined to a narrow zone within L3· Thus, the distinction between innocuous and nociceptive somatosensory events may be encoded, in part, by differences in the spatial distribution, and hence, the relative numbers of spinal neurons activated by nociceptive and innocuous stimuli. The contribution of temporal and spatial factors in encoding the distinction between painful and non-painful sensations was directly evaluated by electrically stimulating axons within the spinal anterolateral quadrant (ALQ) of conscious human subjects. Responses of conscious humans to varying frequencies and intensities of ALQ stimuli indicate that the number of spinal neurons activated by peripheral stimuli and the frequencies at which they discharge are both crucial factors utilized to encode the distinction between innocuous and nociceptive somatosensory events.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
7-23-2026