The torturers of the Inquisition showed the instruments of torture to the prisoner before commencing proceedings, hoping this would be sufficient to extract a "confession". That would surely do the trick for me, as I have an active imagination and, with it, a low threshold for pain.
The normal biological function of pain is to warn us that something is wrong. Severe pain can now be well controlled by drug treatment, but short of this the way we handle pain is very much conditioned by cultural, psychological and physiological factors.
In most peoples' minds, physical pain is closely connected to the concept of courage. Most of us, at one time or another, have challenged ourselves by pondering how we would stand up under torture if something really important was at stake.
For example, how much physical torture could you stand before revealing the hiding place of your friend, knowing that discovery meant certain death?
Such musings are indeed nightmarish in our western culture, which has lost its preoccupation with the high value of physical courage and tolerance of physical pain.
Some cultures greatly prize the ability to tolerate pain. For example, Australian Aborigines practised a ceremony for boys in which coming of age was marked by making a cut along the underneath of the penis.
Various African tribes have customs whereby individuals patiently accept painful procedures such as slitting of skin or insertion of awkward shaped objects under skin.
It was also a cultural expectation amongst American Indian tribes that a warrior captured by another tribe during warfare would courageously bear up under the inevitable subsequent torture. Indeed, traditional Christianity placed a high value on mortification of the flesh and reserved a special place for martyrdom.
People in cultures that habitually endure severe physical hardships have a much better tolerance for pain than the average person accustomed to a Western lifestyle. Himalayan porters, who carry heavy loads for mountain-climbing expeditions at high altitudes were compared to average Americans for their ability to tolerate painful electric shocks. Shocks that elicited howls of anguish from the American subjects failed to excite undue disquiet in the mountain porters, although they did record the jolts as "painful" on written questionnaires.
Also, in some cultures, trepanning, an operation to remove a disc of bone from the skull to reduce pressure on the brain, is performed without anaesthetic.
Low levels of pain are part of normal life, but there is one natural activity which is attended by significant pain - the pain of labour during childbirth.
In the course of our evolutionary history we developed from four-legged creatures into upright two-legged creatures. This development was accompanied by changes in the pelvic structure to allow it to bear more weight. This necessitated a narrowing of the birth canal.
These developments were also accompanied by a rapid increase in brain-size, and, consequently, head-size. This is the origin of the pain of labour - passing the large head of the baby through the relatively narrow birth canal.
Acute pain starts with stimulation of sense receptors in the skin or internal organ. These receptors receive information about events that could cause body damage. Nerve fibres carry the information to the spinal cord which channels it to the brain.
Pain is an important mechanism designed to alert us to a problem so that we will take corrective action. It has to be unpleasant otherwise we would not be sufficiently motivated to carry out remedial action. A small number of people suffer from a condition that precludes them from feeling any pain. At first glance this sounds rather nice, but a moment's thought shows it could have fatal consequences.
Another highly unusual condition is the phantom limb pain syndrome. This is where a subject experiences pain, often intense, in a phantom limb, the original limb having been amputated. This syndrome results from a defect in the signalling system that conveys pain information to the nervous system.
Surprisingly, treating the victim with anti-depressant drugs frequently reduces or removes the "pain" from the phantom limb.
THE mechanism of action of the common drugs used to treat pain sheds light on the chemical processes whereby pain arises in the body. Most of the familiar drugs were originally derived from plants used by various cultures for ages to fight pain.
The most familiar pain-killing drug is aspirin, found in the bark of the willow tree. Aspirin works by inhibiting the synthesis of prostaglandins, chemicals released from cells after injury that cause local pain by interacting with nerve endings.
Cocaine, originally purified from the leaves of the coca plant, is used medically as a local anaesthetic and exerts its pain-killing effect by interacting with the nervous system, inhibiting transmission of pain signals to the brain.
Opium is derived from the poppy plant. Heroin and morphine are well known derivatives of opium. It was discovered in the 1970s that the brain contains receptors for morphine. This receptor is a "lock" which is fitted by the chemical "key" morphine. Because morphine is not natural to the body, the researchers reasoned that, since the brain has receptors for morphine, a substance chemically similar to morphine must naturally exist in the body. Subsequent research discovered the endorphins, natural opiates produced by the brain.
Endorphins are natural painkillers and also produce a sensation of well-being. The ability to secrete endorphins probably varies from person to person, which would explain some of the variation between individuals in ability to tolerate pain.
Studies have also shown that a number of techniques for treating chronic pain, e.g., acupuncture, stimulate the release of endorphins.
William Reville is a senior lecturer in biochemistry and director of microscopy at UCC.