Jefrey Sosa Rodriguez
Estrogen Modulates Sexually Dimorphic Contextual Fear Extinction in Rats through Estrogen
Receptor B
The paper is very intriguing and important to know more from the hippocampus theme. This
paper will help to do experiment in the future and improve the knowledge and the way of doing
the experiments. The authors of this investigation were yao-ju chang, chih-hao yang, ying-ching
liang che-ming yeh, chiung-chun juang,and kuei-sen hsu. The authors compared the brain of
females and males rats. These sex differences occur early during development due to
combination of genetic and hormonal factors and continue throughout the life span. Previous
studies revealed that male rat exhibited significantly and higher level of contextual fear memory
than female rats. It remains unknown whether a sex difference exists in the contextual fear
extinction. To address this issue, male normally cycling female and ovariectomized female
Sprague- Dawley rats were subjected to contextual fear conditioning and extinction trials. Here
we report that although male rats exhibited higher levels of freezing that cycling female rats after
contextual fear conditioning, female rats subjected to conditioning in the proestrus and estrus
stage exhibited an enhancement of fear extinction than male rats. An estrogen receptor B agonist
diarlylpropionitrile but no an ERx agonist propyl-pyrazole-triol administration also enhanced
extinction of contextual fear in OVX female rats, suggesting that estrogen-medicated facilitation
of extinction involves the activation of ERB.
Method:
The method used in this paper are adult male (280-340g) and female (200-240g) dawley rats
were housed in groups of four in a humidity-and-temperature-controlled (24C) vivarium on a 12-
h light-dark cycle (lights on at 7:00 AM) with access to food and water adlibitum. All rats were
acclimated in the animal research facility for at least 7 days prior to use in behavioral
experiments. All effects were made to minimize the number of animals used and their suffering.
In the figure one show the result of the effects of sex on contextual fear conditioning and
extinction. A: Average percent of freezing after conditioned context exposure. Male and cycling
female rats were trained for contextual fear conditioning and tested 24 hours later. Male rats
exhibited significantly higher levels of contextual freezing response that female rats. B: are the
time courses of fear extinction revealed by decrease of freezing response in extinction trials that
are performed on four consecutive days.
Result:
The result of this experiment based in two different themes: The sexually dimorphic contextual
fear conditioning and effects of Ovarian Cycle on Contextual Fear Extinction. The result of
experiment of sexually dimorphic contextual fear conditioning were determined the effects of
sex and ovarian cycle on the acquisition of conditioned fear memory, male and normally cycling
female rats were trained to form contextual fear memory by loading aversive foot shocks in the
conditioning chamber to form contextual fear memory by loading aversive foot shocks in the
conditioning chamber. At 24 hour after conditioning, rats were re-exposed to the conditioning
chamber for 3 minutes without foot shock and the levels of freezing response were scored. Al l
already observed female rat’s exhibit significantly lowest levels of contextual freezing response
than male rats. Found no differences among cycling females brats in proestrus and diestrum
stage. On other hand, in the effects of ovarian cycle on contextual fear extinction examined the
effect of sex and ovarian cycle on extinction of contextual fear. Male and normally cycling
female rats were subjected to daily extinction trial on four consecutive days. The females rats
subjected to conditioning in the proestrus stage exhibited more rapid contextual fear extinction
than vehicle treated rats across the trials. Females rats treated with progesterone showed similar
contextual fear conditioning.
Discussion:
This study revealed the existence of a sex differences in the rate of contextual fear extinction.
Three major findings were obtained. One of this is that the female rats subjected to conditioning
in the proestrus and estrus stages exhibited an enhancement in the rate of contextual fear
extinction than male rats. The second is that the estradiol can effectively promote the contextual
fear extinction in OVX female rats. The third, intra-hippocampal injections of estradiol (sexual
female hormone that help the envelope of female) agonist enhanced the retrieval of contextual
fear extinction. Indeed, female rats extinguished their fear more rapidly than male rats in a more
intense conditioning training paradigm, which induced maximal contextual freezing responses in
both sexes. Given that females rats subjected to conditioning in the diestrus stage exhibited a
similar extinction rate as male rats changes in the levels of circulating steroids across the ovarian
cycle may account for the sex difference favoring females in the contextual fear extinction. I
agree to this experiment, because for that results will produce some medicine to fight several
disorders brain and nervous system.
References:
1) jneurosci.org/cgi/content/full/27/36/9729, Estrogen Disrupts the Inhibition of Fear in
Female Rats, Possibly through the Antagonistic Effects of Estrogen Receptor
(ER )
and ERß, Donna J. Toufexis, Karyn M. Myers, Michael E. Bowser, and Michael Davis,
Endocrinology 139:4513–4522.
Yao-ju Chang, Chih-hao Yang, Ying-Ching Liang Che-ming Yeh, Chiung-Chun Juang,and kueisen Hsu, Estrogen Modulates Sexually Dimorphic Contextual Fear Extinction in Rats through
Estrogen Receptor B,2009,march 31.