Biology 202, Spring 2005
Second Web Papers
On Serendip

Through my extensive research I came to the key question, why is pain different in everybody? An article, Gender Differences in Brain Response to Pain, suggests that the brain difference to pain within males and females goes back to more primitive times because the roles of men and women were clearer. The responses of men and women to the same pain stimuli were different. The women's limbic region, the more emotional area, showed more activity than in males. The male's cognitive regions showed more activity than in females. Since the women's limbic region has the most activity when in pain might be a result of women's nurturer instinct which is more emotional. The male's activity within the cognitive region, when in pain, could be a result of their inherent fight-or-flight reaction (1).

This study gave some insight into the differences of pain between men and women, but just was not convincing enough. The next experiment I discuss seems to give me a clearer and more convincing answer to why men and women feel pain differently.

Scientists have recently posted articles that show that gender, sex hormones, and genes play an important part to how one's body and emotions react to pain (2). It is interesting to me that scientists are finally able to understand how the brain functions through monitoring the chemical activity within the brain while one is in pain. This is done by to monitoring the brain using fMRI and position-emission tomography(PET) while one is in pain.

Many studies have been done, one specifically testing controlled pain in men and women while being monitored. Researches at the University of Michigan have been studying the affects of pain on the brain. Their recent studies suggest that mu-opiod receptors and endorphins are crucial to one's ability to feel pain. Scientists have been studying the mu-opioid receptors which are found through out the brain. The mu-opioid receptors are what needs to be activated by endorphins (natural/synthetic) to help relieve pain. If these receptors do not have anything to activate them to bind then they are unable to block pain. With this information the scientists began their study. (2).

The scientists used and injection of salt-water into the masseter muscle to stimulate pain known as temporomandibular joint pain (TMJ). This pain was sustained and did not have much physical and psychological stress on the person. Throughout the whole process the people were monitored through PET and were also asked to rate their pain. 14 men and 14 women were part of this experiment having the same procedure done to them. (2).

The scientists monitored each person's brain through fMRI and position-emission tomography (PET) while they were in pain. The pain was controlled through injections so that the pain would be constant at all times within each subject. The data showed that the women were more likely to be in more physical and emotional pain than men. This was monitored through the PET which showed that men released more endorphins than the women. The women actually had a reduction of endorphin release. Scientists say this is because all the women being tested were on their menstrual cycle which meant that their estrogen levels were low and an able to release endorphins efficiently. (2).

Another study was done showing that women with high estrogen levels dealt with pain much better than women with low estrogen levels. This experiment was done using the same injection of salt-water to the masseter muscle in women during their menstrual cycle. The women where to wear an estrogen patch, which would increase their estrogen levels towards the end of their menstrual cycle so that they could be monitored with an increase in estrogen, but none of the other hormones changed. Their brain's were studied while in constant pain and the amount of endorphins released while women had high energy levels was significant enough that their responses to the pain was more like the men's responses to pain. This suggests that women are more prone to feeling pain than males, but are able to regulate their pain level with hormones. (2).

The findings suggest that women are more likely to have pain during their monthly menstrual cycle or during pregnancy because of the variations of their estrogen levels. The estrogen levels they are unable to block the feeling of pain. regulate the brain's ability to suppress pain. When the estrogen is high, the brain is more capable of releasing endorphins to help reduce the pain. When the estrogen levels are low, like during one's menstrual cycle/ pregnancy, the brain does not release endorphins efficiently to reduce pain. (2).

This study is interesting because it raises a lot of other questions about women and why we are more susceptible to pain. It gives us a grasp on why we might be experiencing more pain than males and how to go about reducing the pain. Women and men have men differences that set them apart. Will there ever be a way to make males and females equal?

References

1)Pain and the brain:
Sex, hormones & genetics affect brain's pain control system, shaping a person's pain perception, U-M research finds,

2)Gender Differences In Brain Response To Pain,


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