Effects of Estradiol on the

Inflammatory Response in Female Rats

Presentation by: Sherina LangdonMentor: Dr. Vanya QuinonesPsych 396 Honor Thesis

WHY DO WE FEEL PAIN?• Pain is a signal that the body has

been damaged or something is wrong.• The spinal cord is the main route for

all pain messages to the brain, where pain is then registered.

PAIN STUDIES• Pain studies have found that women

are more likely than men to report and demonstrate higher pain sensitivity.

• In rats, females display higher pain scores in inflammatory pain than males do.

PAIN STUDIES• Clinical evidence has shown that

sensitivity thresholds in women in response to a variety of painful stimuli is dependent upon menstrual cycle phase, tissue type, and plasma sex steroid levels.

• Ovarian hormones have been targeted to be the basis for the health disparity between male and females.

PREVIOUS STUDIES• Involved researching sex differences in

humans in their responsiveness to painful stimuli.

• Sex differences in the response to pain in rats

• Estradiol effects of the inflammatory response to formalin in female rats

HYPOTHESIS• The hypothesis of this research is

that ovariectomized female rats, which have no estradiol, will demonstrate more pain as opposed to the ovariectomized female rats that receive estradiol injection.

PRODECURES SO FAR• Eight-week old ovariectomized rats are divided

into groups: Naïve group: no injection (control group), Estradiol group: Rats received Silastic surgery of estradiol, Cholesterol group: Rats received Silastic surgery of cholesterol.

PROCEDURES SO FAR• The next step is behavioral testing using

Hargereaves Paw Thermal Simulator. The rats acclimate on the simulator for 30 minutes and then the Baseline Reading (records Paw Withdrawal Latency, P.W.L) is recorded before any injections are made.

• Then Saline, control group, or Carrageenan, experimental group are injected in the female rats and then we either wait, 1 hour, 5 hours or 24 hours before we test the P.W.L again

WHAT IS CARRAGEENAN?• Carrageenan is made from parts of

various red algae or seaweeds and is used for medicine. • Carrageenan is used in research labs

to intentionally induce inflammation in the intestinal cells of lab animals

HARGREAVES PAW THERMAL SIMULATOR

SALINE PAW VS. CARRAGEENAN PAW

SALINEINJECTI

ON

CARRAGEENANINJECTION

PRODECURES CONTINUE• The rats are then sacrificed by

decapitation. Next, we remove the spine and brain. We dissect the tissue at the lumbar region of spinal cord and Dorsal Root Ganglion. We then slice the tissues using a cryostat.

CYROSTAT

HYPOTHESIS• The hypothesis of this research is

that ovariectomized female rats, which have no estradiol, will demonstrate more pain as opposed to the ovariectomized female rats that receive estradiol injection.

RESULTS• T-tests were performed and so far our data and

interpretations are the following: • The group of rats that received cholesterol has a

higher mean value than the estrogen group, which indicates greater astrocyte proliferation. This increase in proliferation is linked to greater inflammation. This is left unmediated by estrogen, which suggests that estrogen is in fact anti-inflammatory.

RESULTS• The group of rats that received carrageenan and

estrogen (CgE) have a significantly lower mean value than the saline and cholesterol groups (SCH), which indicates that although the carrageenan caused inflammation, estrogen attenuated this inflammation.

• This data suggests that estrogen is anti-inflammatory and that it promotes lower astrocyte proliferation and lower inflammation.

RESULTS• The SCH groups have a higher mean value

than the SE groups and the CgCH groups have a higher mean value than the SE groups.

• This data also indicates greater astrocyte proliferation and suggests that estrogen is anti-inflammatory.  

CONCLUSION• In conclusion, the comparison of cholesterol-

treated rats and the estrogen-treated rats revealed that there was a significant difference in the astrocyte mean area; and that the estrogen-treated rats had a significantly lower astrocyte mean then that of the cholesterol-treated rats.

• These results cooperate with the hypothesis, that ovariectomized female rats, which have no estradiol, will demonstrate more pain as opposed to the ovariectomized female rats that receive estradiol insertion. SCH groups have a higher mean value than the SE groups and the CgCH groups have a higher mean value than the SE groups.