Pain: the Good, the Bad, and the Ugly

            According to the International Association for the Study of Pain (IASP), pain has been described as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” (IASP website) It is our body’s way of communicating that something is wrong; either the body has come in contact with an external noxious stimuli or a noxious stimuli has been introduced to the body, causing potential harm. There are specific cells in the body that are responsible for sensing noxious stimuli; they are called nociceptors. Nociceptors are specific neurons designed specifically for three actions:

1)                  to detect the mechanical, thermal and/or chemical noxious stimuli that can impinge on the body;

2)                  to transduce those mechanical, thermal and/or chemical signals into meaningful electrical/chemical signals that the nervous system can understand; and

3)                  to transmit those electrical/chemical signals to the spinal cord for quick, appropriate action and to the brain for processing.

These three actions, together, are the properties of nociception.

            In many cases, the pain resulting from the site of injury can last for hours, or even days, after the injury as occurred. This is due to sensitization, which  is the heightened sensitivity of nociceptors following tissue damage. When a noxious stimuli comes in contact with the body, a number of things are happening:

1)                  the nociceptors become even more sensitive to stimuli;

2)                  chemicals are spilled from damaged cells, including prostaglandin, which when released from cells is very painful;

3)                  blood-borne chemicals, such as histamine, is introduced to the area and causes itching or other allergic reactions; and

4)                  chemicals are released from active nociceptors. All of this is happening in the inflammatory exudate, the area where injury has occurred and where pain is still occurring.

            There have been many advances in pain psychology towards the understanding of how the human brain processes pain. The very first theory is known today as the Specificity Theory. The Specificity Theory, thought of by a German physiologist named Müller, suggested that the body had its own sensory system specifically for pain perception and that this sensory system has its own  nerves, its own pathways, its own receptors, and its own location in the brain. Later, the Pattern Theory, by von Frey, came into play. This theory suggested that nociception was simply a unique pattern of activity in non-specific peripheral cells (the dendrites of neurons). (Willis and Coggeshall, 1994) Although these theories seemed to make sense when they were formed, there were a number of issues that these theories failed to address. Neither the Specificity Theory nor the Pattern Theory could be used to address:

1)      chronic pain and why it outlasts the presence of noxious stimuli.

2)      the link between nociception and pain. For example, why do we experience pain even in the absence of noxious stimuli?

3)      localization. For example, the location of the pain may vary or differ from the site of injury.

4)      how the nature of pain changes over time. For example, the site of injury may be more painful just a few  hours after injury, but it may not hurt as much 3 days after injury.

Because these theories lacked in explaining the above mentioned questions, Melzack and Wall (1965) formulated the Gate Control Theory, which is still the leading theory used today to explain how pain is processed by the body.  In this theory, larger nociceptors (Aβ and Aα fibers) are stimulated by low-intensity stimuli and excite nociception pathways to the spinal cord and brain, while smaller nociceptors (Aδ and C fibers) are stimulated by high-intensity stimuli and both excite and inhibit nociception to the spinal cord and brain. The theory suggests that it is a summation of activity from both small and large fibers that will finally send information regarding pain to the spinal cord and brain. Although this theory was constructed in response to the Specificity Theory’s and Pattern Theory’s limitations (mentioned above), it cannot be used to address all questions in regards to how we process pain. (Willis and Coggeshall, 1994) For example, does not address why we can still feel pain even in the absence of noxious stimuli (point #2 above).

            Measuring pain can be essential for many reasons. Pain measurements can tell us where the pain is localized in relation to the site of injury, what tissue(s) is(are) damaged and how a physician or surgeon can go about treating the pain and/or damaged tissue. Pain can be measured in many ways, but the best method to use really depends on the age of the individual who is in pain. Adults can assess their pain using the McGill pain questionnaire and Present Pain Index (PPI). These methods ask you to describe you pain on a scale of 0-10 with 0 being no pain at all and 10 being the worst pain imaginable. The questionnaire also asks to choose words that describe your pain, such as scraping, excruciating, throbbing, tightening, etc. Children, on the other hand, are not as familiar with this high-level of vocabulary, and because of this the Faces Scale can be used to assess their pain. The faces of the Faces Scale range in emotion from very happy to very sad; the children can pick the face that best represents how they are feeling at that time. Babies are even more difficult to assess in regards to pain intensity; because they cannot speak, circle vocabulary words, or even point to faces, we must measure their pain in other ways. The Face, Legs, Activity, Cry, and Consolability (FLACC) Scale measures movements of the face and legs, measures the intensity of the baby’s cry and activity, and measures how well a baby can be consoled if picked up and rocked. The higher the score for the FLACC test, the more pain the baby is experiencing.  With these methods of measuring pain, doctors can get a better idea of how to go about treating an individual who is experiencing the pain.

            Pain, just like any other emotion, is very subjective and its intensity can range from one individual to the next. Psychologists tend to use the Biopsychosocial Model to explain the variables that influence how an individual experiences pain. This model says that variances in pain perception from one individual to another are due to biological, sociocultural, and psychological differences between people. Biologically, there may be differences because of gender, genes, or ethnicity. For example, although there is not enough research to prove this, many assume that women have a higher pain threshold than men can because they can undergo childbirth. With respect to culture, individuals in different parts of the world see pain differently than other people do. An example would be a man in the Middle East whose faith allows him to walk on a long stretch of fire-hot glass and coal without experiencing pain, while a man in the United States feels pain at just the thought of walking on hot coal and glass. Lastly, psychological factors, such as depression and other neurological disorders (such as schizophrenia) can have an effect on how thinks about pain. Although we would like to simplify how we understand pain and how pain perception can be influenced, we cannot blame only one aspect of the Biopsychosocial Model; the three aspects of the model are intertwined and one cannot be used to justify pain experiences without mentioning the other two.

            We can treat pain using various methods. Drugs, such as opiates or no-opiate medications (such as aspirin or ibuprofen), can be used orally to alleviate pain. Other, more non-traditional, methods include, but are not limited to, acupuncture and talk therapy.

            My partner, Dan Logan, and I wanted to talk about many controversial topics regarding pain and the pain experience. After completing our research, we came up with some interesting questions that we, alone, did not have answers to, but wanted to take to the classroom to get the opinions of others on. The topics and the questions behind them are as follows:

·         Should we be more liberal with how we treat pain? Using opiates? Using physician-assisted suicide?

·         How controversial are these statements regarding sex and cultural differences in pain perception? Agree? Disagree?

·         If IASP describes pain as “an unpleasant sensory and emotional experience”, why is it that some individuals enjoy the thrill of cutting themselves (or harming themselves)?

·         What would happen if we ended pain entirely? Pain does have its advantages!

·         Have we changed our views on the use of animal models for scientific research? They, too, feel pain.

            Not all of the above topics/questions were discussed during class that evening or mentioned in depth on the online course forum, however a couple of the topics were addressed in both areas of discussion. In summary, it was felt that animals, especially, those with a conscious (humans), do have the fundamental right to be pain-free. Although pain, as a medical condition, has not been taken seriously until relatively recently, we now think about pain as any other condition that needs relieving and we treat it using drugs, even opiates. Although we feel that opiate-use should still be monitored by the appropriate authorities, we feel that relief from pain should be made a priority and that if opiate-use is what works for one’s pain, than the individual has every right to have opiate prescriptions and should not be denied it.  In regards to physician-assisted suicide, on the other hand, rather touchy ethical and religious discussions tend to come up, making this practice more and more controversial. However, what I, as well as some others, learned was that physician-assisted suicide is, in fact, legal in some states, such as Oregon, under the “Death with Dignity Act”.

            Lastly, many members of the class feel that it would not be wise to take away pain perception completely. Although we do agree that if one is in pain, he or she has the right to end the suffering with the use of drugs, acupuncture, or even talk therapy, we should not do anything to our bodies that would completely disable us from being able to experience pain. This would be too dangerous and would put the body at a higher risk for illness and injury because we would not be able to perceive if and when noxious stimuli were around to harm us.

            All in all, I feel that the discussion on the biological and psychological basis of pain and pain perception went very well in our class discussion. Not only did we talk about some intriguing and controversial topics, we also learned some new information, together, and added on some new thoughts to our previous understandings of pain.

le Bars, D, Gozariu M, Cadden SW. 2001. Animal Models of Nociception. Pharmacological Reviews 53, 597-652

Haig, Scott. “How Real is Your Pain?” Time Magazine Online. Accessed on April 1, 2008. Updated on February 20, 2007. http://www.time.com/time/printout/0,8816,159,1681,00.html

“IASP Pain Terminology”. International Association for the Study of Pain. Accessed on Wednesday, April 30, 2008. http://www.iasp-pain.org/AM/Template.cfm?Section=Pain_Definitions&Template=/CM/HTMLDisplay.cfm&ContentID=1728

Julius D and Basbaum, AI. 2001. Molecular mechanisms of nociception. Nature 413, 203-210

Mogil JS, Chesler EJ, Wilson SG, Juraska JM, Sternberg WF. 2000. Sex differences in thermal nociception and morphone antinociception in rodents depend on genotype. Neuroscience and Biobehavioral Reviews 24, 375-389

Smith K. 2007. Brain waves reveal intensity of pain. Nature 450, 329