https://science.sciencemag.org/content/sci/150/3699/971.full.pdf

Pain mechanisms: a new theory.

The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat

Well-being : the foundations of hedonic psychology

A peripheral mononeuropathy was produced in adult rats by placing loosely constrictive ligatures around the common sciatic nerve. The postoperative behavior of these rats indicated that hyperalgesia, allodynia and, possibly, spontaneous pain (or dysesthesia) were produced. Hyperalgesic responses to noxious radiant heat were evident on the second postoperative day and lasted for over 2 months. Hyperalgesic responses to chemogenic pain were also present. The presence of allodynia was inferred from the nocifensive responses evoked by standing on an innocuous, chilled metal floor or by innocuous mechanical stimulation, and by the rats' persistence in holding the hind paw in a guarded position. The presence of spontaneous pain was suggested by a suppression of appetite and by the frequent occurrence of apparently spontaneous nocifensive responses. The affected hind paw was abnormally warm or cool in about one-third of the rats. About one-half of the rats developed grossly overgrown claws on the affected side. Experiments with this animal model may advance our understanding of the neural mechanisms of neuropathic pain disorders in humans.

A peripheral mononeuropathy in rat that produces disorders of pain sensation like those seen in man.

As humans, we perceive feelings from our bodies that relate our state of well-being, our energy and stress levels, our mood and disposition. How do we have these feelings? What neural processes do they represent? Recent functional anatomical work has detailed an afferent neural system in primates and in humans that represents all aspects of the physiological condition of the physical body. This system constitutes a representation of 'the material me', and might provide a foundation for subjective feelings, emotion and self-awareness.

How do you feel? Interoception: the sense of the physiological condition of the body.

(1979). Substantia gelatinosa and the control of somato-sensory transmission. International Rehabilitation Medicine: Vol. 1, No. 3, pp. 106-110.

Substantia gelatinosa and the control of somato-sensory transmission.

RECENT studies have revealed the existence of endogenous morphine-like compounds in the central nervous system1–3 and in the pituitary4. These compounds, named enkephalin1 and C-fragment4, have been reported to produce analgesia when injected intraventricularly in rats and cats5,6 and to be antagonised by naloxone which is a potent antagonist of narcotic analgesics. They also have a high affinity for the opiate receptor, which has been discovered in the central nervous system of vertebrates including man7, and they can displace naloxone from these receptors2–4. There is substantial evidence that central grey structures in the midbrain are intimately involved in analgesia. Electrical stimulation8 and microinjection of morphine9,10 in these regions produce analgesia which is antagonised by naloxone. Stimulation of the central grey region in humans11 has been reported to produce marked analgesia which is antagonised by small doses of naloxone12. In addition, acupuncture analgesia has been reported to be antagonised by naloxone13. These findings have led to the hypothesis that there may be an ongoing release within the brain of a morphine-like compound which is partially responsible for pain thresholds. If this were so, then the antagonism of the effects of the endogenous compound by naloxone should affect pain perception. The experiments reported here demonstrate that the perception of experimentally induced pain in normal human subjects is not altered by administration of the opiate antagonist naloxone.

Lack of effect of naloxone on pain perception in humans

Publisher Summary This chapter discusses the details of pain mechanisms that provide a possible probe into the functional conditions under which the brain varies the thresholds and intensities of reaction to an injury. Pain is that sensory experience evoked by stimuli that injures or threatens to destroy tissue. Pain is composed of, first, a separate and distinct sensation and, second, the individual's reaction to pain. The adequate stimulus for pain is the rate of destruction of a tissue innervated by pain fibres. Biologists recognize that those stimuli that cause pain are liable to damage tissue. The unmyelinated afferent sensory fibres contain a large population of fibres responding only to injury or to intense pressure, temperature, or chemical stimuli. For this reason and many others, there has been a general acceptance that the unmyelinated afferent sensory fibres play a major role in triggering pain. There is no doubt that all of the spinal cord cells that are candidates for transmitting information about injury are affected both by convergent impulses from non-noxious stimuli in the periphery and by descending systems from the brain.

Have the authors addressed themselves to the topic “pain mechanisms in the spinal cord”?

Noordenbos was a key figure in the present renaissance of the attack on the problem of pain. The evidence for this assessment is his book ‘Pain’ published by Elsevier in 1959. This seminal slim 180 page volume is subtitled with his typical modesty ‘A preliminary statement.’ It launched the present era with 3 highly original innovations. First he introduced methods of clinical examination which allowed the patients to indicate their feelings without forcing them into one of the traditionally acceptable types. This liberated the patient from his previous task of assuring the

William Noordenbos 1910–1990☆

Local application of capsaicin to one sciatic nerve induces profound changes in peptide-containing afferent fibres in the ipsilateral lumbar dorsal horn of the adult rat

Patrick D. Wall

Papers

Substantia gelatinosa and the control of somato-sensory transmission.

Lack of effect of naloxone on pain perception in humans

Have the authors addressed themselves to the topic “pain mechanisms in the spinal cord”?

William Noordenbos 1910–1990☆

Local application of capsaicin to one sciatic nerve induces profound changes in peptide-containing afferent fibres in the ipsilateral lumbar dorsal horn of the adult rat