Abstract
A multitude of sensations are experienced as a consequence of the wide range of external stimuli that impinge upon the body surface. In spite of this diversity a simple distinction can readily be made for each individual sensation, is it painful or not? The relationship between stimuli that produce painless or painful sensations is not however fixed. After injury, stimuli that would normally not be expected to produce pain can begin to do so. This is the phenomenon of post injury pain hypersensitivity or hyperalgesia. If we examine the relationship between stimulus intensity and the sensory responses evoked (Fig. 1) we see firstly that beyond the threshold for detecting the stimulus (St) there is a range of stimulus intensities (b) that produce increasing but non-painful sensations. At a certain critical point the stimulus intensity reaches a level where the sensation changes from being painless to being painful (the pain threshold, Sp). Further increases in stimulus intensity ultimately injure the tissue (Si). The range of stimuli that exceed Sp are effectively what we call noxious (c in Fig. 1) , and are characterized as being potentially or actually damaging to the tissue. Stimuli below these intensities (a and b) are innocuous and are never damaging. This relationship is sufficiently robust that we can normally easily predict from a potential stimulus, whether it is likely to be painful or not, and is a reflection of the specificity of function of primary sensory neurons.
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References
Brown, A.G. and Fyffe, R.E.W. (1981). Form and function of dorsal horn neurons with axons ascending the dorsal columns in the cat. J Physiol. Lond. 321 31–47.
Cook, A.J., Woolf, C.J., Wall, P.D. and McMahon, S.B. (1987). Dynamic receptive field plasticity in the dorsal horn of the rat spinal cord following C-primary afferent input. Nature 325 151–153.
De Biasi, D. and Rustioni, A. (1988). Glutamate and Substance P coexist in primary afferent terminals in superficial laminae of the spina; cord. Pro. Natl. Acad. Sci. (USA), 85 7820–7824.
Hylden, J.L.K., Nahin, R.J., Traub, R.J. and Dubner, R. (1989). Expansion of receptive fields of lamina I projection neurons in rats with unilateral adjuvant-induced inflammation: the contribution of dorsal horn mechanisms. Pain, 37 229–244.
Jahr, C.E. and Yoshioka, K. (1986). la afferent excitation of motoneurones in the in vitro new born rat spinal cord is selectively antagonised by Kynureate. J. Physiol. (Lond). 370 515–530.
King, A.E., Thompson, S.W.N., Urban, L. and Woolf, C.J. (1988). The responses recorded in vitro of deep dorsal horn neurones to direct and orthodromic stimulation in the young rat spinal cord. Neuroscience 27 231–242.
King, A.E., Thompson, S.W.N., and Woolf, C.J. (1989). Activation of ventral horn neurones by peripheral nerve and skin stimulation in the rat isolated spinal cord-hindlimb preparation. J.Physiol. (Lond). 412, 25P.
Mendell, L.M. (1966). Physiological properties of unmyelinated fibre projections to the spinal cord. Exp. Neurol. 16 316–332.
McCarthy, P.W. and Lawson, S.N. (1989). Cell type and conduction velocity of rat primary sensory neurones with substance-P like immunoreactivity. Neurosci. 28 745–753.
Meyer, M.L., Westbrook, G.L. and Guthrie, P.B. (1984). Voltage dependent block by Mg2+ of NMDA responses in spinal cord neurons. Nature, 309 261–263.
Price, D.D., Hayes, R.L., Ruda, M. and Dubner, R. (1978). Spatial and temporal transformation of input to spinothalamic tract neurones and their relation to somatic sensations. J.Neurophysiol. 41 933–947.
Raja S, Cambell, J N, and Meyer R A (1988). Peripheral mechanisms of somatic pain. Anesthesiology, 68. 571–590.
Ryu, P.D., Gerber, G., Murase, K. and Randic, M. (1988). Actions of calcitonin gene-related peptide on rat spinal dorsal horn neurons. Brain Res. 441. 357–361.
Schaible, H.G., Schmidt, R.F. and Willis, W.D. enhancement of the responses of ascending spinal tract cells in the cat spinal cord by acute inflammation of the knee joint. Exp. Brain Res. 66 489–499, 1987.
Schneider, S.P. and Perl, E.R. (1988). Comparison of primary afferent and glutamate excitation of neurons in the mammalian spinal dorsal horn. J. Neurosci. 8 2062–2073.
Urban, L. and Randic, M. (1984). Slow excitatory transmission in rat dorsal horn, possible mediation by peptides. Brain Res. 290 336–341.
Woolf, C.J. (1983) Evidence for a central component of postinjury pain hypersensitivity. Nature, 306 686–688.
Woolf, C.J. and King, A.E. (1987). Physiology and morphology of multireceptive neurones with C afferent fibre inputs in the deep dorsal horn of the rat lumbar spinal cord. J.Neurophysiol. 58. 460–479.
Woolf. C.J. and King, A.E. (1988). Subliminal fringes and the plasticity of dorsal horn neurons receptive field properties. Soc. Neurosci. Abst. 14. 696.
Woolf C.J., and King, A.E. (1989). Subthreshold components of the receptive fields of dorsal horn neurones in the rat. J. Neurophysiol. In Press.
Woolf, C.J. and McMahon, S.B. (1985). Injury-induced plasticity of the flexor reflex in chronic decerebrate rats. Neuroscience. 16 395–404.
Woolf, C.J. and Wall, P.D. (1986). The relative effectiveness of C-primary afferent fibres of different origin in evoking a prolonged facilitation of the flexor reflex in the rat. J. Neurosci., 6 1433–1442.
Woolf, C.J., Chong, M.S. and Rashdi, T. (1985). Mapping increased glycogen Phosphorylase activity in dorsal root ganglia and in the spinal cord following peripheral stimuli. J. Comp. Neurol., 234 60–76.
Woolf, C.J., Thompson, S.W.N. and King, A.E. (1989). Prolonged primary afferent induced alterations in dorsal horn neurones; an intracellular analysis in vivo and in vitro. J.Physiol de Paris, (in press).
Yoshimura, M. and Jessell, T.M. (1987). Membrane properties and afferent evoked synaptic responses of substantia gelatinosa neurones in rat spinal cord slices. Neurosci.Abstr. 13 1389.
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Woolf, C.J., Thompson, S.W.N. (1991). Slow Potentials, Receptive Field Plasticity and Pain. In: Franzén, O., Westman, J. (eds) Information Processing in the Somatosensory System. Wenner-Gren Center International Symposium Series. Palgrave, London. https://doi.org/10.1007/978-1-349-11597-6_32
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