Can Neuroscience Validate the Excuse “Not Tonight, Dear, I have a Headache?"

Men
and women experience fluctuations in sexual motivation over a lifetime. Whether
sexual desire is enhanced or diminished at any particular time can depend on a
number of factors and circumstances, but researchers from McGill University
recently set out to determine specifically how pain impacts sexual behavior.¹ Results from this study, published in The Journal of Neuroscience earlier this
year, were the topic of the most recent “Neuroethics and Neuroscience in the
News” discussion facilitated by Emory Women’s
Gender and Sexuality graduate student Natalie Turrin and Neuroscience
graduate student Mallory Bowers.




To study how pain impacts sexual
motivation, researchers used a partitioned Plexiglas chamber where the
partition contained small, semi-circular openings only large enough for the
female mice to pass through (this study required that male mice be greater than
45 g and female mice smaller than 25 g). In this set-up, the females were free
to either cross the partition and engage in sexual activity with the male mice
or “escape” to the side where the males were unable to follow. Sexual
motivation in this study was measured by how many total mounts occurred, and since
mounting involves male participation, time spent on the male side of the
chamber was also a measure of female sexual motivation. When researchers
injected female mice with inflammatory agents in the vulva, hind paw, tail, or
cheek to induce pain, female mice consistently participated in less mounting
behavior and spent less time on the male side of the cage compared to no
injections. Males, on the other hand, when injected with the same inflammatory
agents in either the penis, hind paw, tail, or cheek, experienced unimpeded
sexual activity (total number of mounts did not decrease compared to controls) in
an open field paradigm where the males had unrestricted access to the females. Although
it has been observed that female mice can have a higher sensitivity to pain
than male mice,² researchers observed that male and female
mice exhibited the same level of sensitivity towards inflammation to the hind
leg according to the mouse grimace scale (MGS), a visual observation of a mouse’s facial
features to determine pain levels.




The final experiments to study sexual
activity involved rescuing the lack of sexual motivation from female mice using
either an antinflammatory agent or two different prosexual drugs. The analgesic
pregabalin reversed the reduction of total mounts that resulted from inducing
pain in females, and according to the MGS, also reduced the level of pain. “Prosexual”
drugs, apomorphine (APO) and melanotan-II (MT-II), had the same rescuing effect,
but based on the MGS, did not have the ability to relieve pain from the
inflammatory injections. It should be noted though that APO increases
locomotion³ in mice, which may partially account for
the females moving towards the male side of the cage more often.




From these experiments, researchers
concluded that female mice have lower levels of sexual motivation when in pain,
but even in penile pain, male mice maintain a desire to participate in sexual
activity. However, the decrease in sexual motivation can be rescued in females
by either pain reduction or aphrodisiacs,
in this case a dopamine agonist (APO) or an α-melanocyte-stimulating hormone
analog (MT-II). Perhaps these claims made regarding mice are reasonable, but it
is even more problematic that the authors confidently extrapolate the results
to humans. The final line of the abstract reads “These findings suggest that the well known context sensitivity of the
human female libido can be explained by evolutionary rather than sociocultural
factors, as female mice can be similarly affected.”




Of course, media outlets ran with this
conclusion and multiple articles were published with definitive titles like “Women ARE more likely to go off sex when
they are in pain” and “That headache excuse is real: For females,
pain kills sexual desire.”
The authors of this paper perpetrated the idea that a woman’s lack of sexual
motivation at any given moment is
either a biological or
a sociocultural one. In the press release and the paper, the authors refer to the
apparently common aphorism “Not tonight, dear, I have a headache,” and mention
that this would be evidence that sometimes wives are in too much pain to have
sex that has been initiated by their husbands. But sexual relations are so much
more complicated than just a simple relationship such as a pain from a headache
equals lack of sexual motivation. What if the woman (or man, for that matter)
doesn’t really have a headache, but there is another underlying reason that a
partner is too embarrassed to share? Or, what if pain from a headache makes you
feel less sexy, and that feeling is the sexual deterrent, not the pain alone? Pain,
either directly or indirectly, would most likely make a person feel less
sexual, but why does is take a study with mice (who aren’t insecure about love
handles or annoyed with a spouse due to an insensitive comment) to validate
this thought? It is reminiscent of neuro-realism, the
idea that attaching a brain scan to any study or correlation suddenly qualifies
the findings as real or more true.⁴ While this study only involved mice,
researchers did use fMRI to study the difference between the brains of women
with and without acquired hypoactive sexual desire disorder (HSDD) in this paper.⁵ But no one - including females, their sexual
partners, researchers, or doctors - really wins when it is being advertised
that the female libido is something that can be can characterized as either
biologically or socioculturally driven. 

Via The Telegraph

One reason for ascribing a biological reason
to the lack of sexual motivation could involve drug development; if a
biological target can be found that is responsible for diminishing sex drive,
then perhaps there is a pill to fix that. The work in the paper was supported
by a Pfizer Pain Research Award from Pfizer Canada, and Pfizer Canada did
kindly provide the pregabalin that was used in the sexual recovery research. There
have been a number of pharmaceutical companies that have sought FDA approval
for low female sexual desire,⁶ even when the diagnosis of disorders such as
HSDD and female sexual dysfunction (FSD) are controversial. One example though
is Lybrido, a drug meant to treat HSDD. (Mallory actually gave a journal club talk last year about the implications of pharmaceutical
companies targeting the female sex drive with a focus on Lybrido). Lybrido
is interesting because it was ineffective in a cohort of women who “suffer from
HSDD as a result of inhibitory mechanisms,” resulting from negative
associations with sex and for that reason Lybridos was developed.⁷ Lybidos has an additional
component that targets the prefrontal cortex areas of the brain and is meant to
alleviate these inhibitory mechanisms.⁸ A discussion of drug
development for women that have negative associations with sex is beyond the
scope of this post, but the mentality that this could be relieved with only a
pill is grossly overly simplifying the complexities of the female libido and
how this affects relationships women have with their sexual partners. If
researchers in academia though are willing to commit to the idea that female
sexuality can be classified as solely biologically determined, then can we
really expect that pharmaceutical companies, marketing campaigns, and sensationalized
news articles won’t try to capitalize on that idea?

Via The Neurocritic

References 

(1)  Farmer, M. A.; Leja, A.; Foxen-Craft,
E.; Chan, L.; MacIntyre, L. C.; Niaki, T.; Chen, M.; Mapplebeck, J. C. S.;
Tabry, V.; Topham, L.; Sukosd, M.; Binik, Y. M.; Pfaus, J. G.; Mogil, J. S.
Pain Reduces Sexual Motivation in Female But Not Male Mice. J. Neurosci.
2014, 34, 5747–5753.

(2)  Mogil, J. S. Sex
Differences in Pain and Pain Inhibition: Multiple Explanations of a
Controversial Phenomenon. Nat. Rev. Neurosci. 2012, 13,
859–866.

(3)  Horn, C. C.;
Kimball, B. A.; Wang, H.; Kaus, J.; Dienel, S.; Nagy, A.; Gathright, G. R.;
Yates, B. J.; Andrews, P. L. R. Why Can’t Rodents Vomit? A Comparative
Behavioral, Anatomical, and Physiological Study. PLoS ONE 2013, 8,
e60537.

(4)  Racine, E.; Bar-Ilan,
O.; Illes, J. fMRI in the Public Eye. Nat. Rev. Neurosci. 2005, 6,
159–164.

(5)  Woodard, T. L.;
Nowak, N. T.; Balon, R.; Tancer, M.; Diamond, M. P. Brain Activation Patterns
in Women with Acquired Hypoactive Sexual Desire Disorder and Women with Normal
Sexual Function: A Cross-Sectional Pilot Study. Fertil. Steril. 2013,
100, 1068–1076.e5.

(6)  Shames, D.; Monroe,
S. E.; Davis, D.; Soule, L. Regulatory Perspective on Clinical Trials and End
Points for Female Sexual Dysfunction, in Particular, Hypoactive Sexual Desire
Disorder: Formulating Recommendations in an Environment of Evolving Clinical
Science. Int. J. Impot. Res. 2006, 19, 30–36.

(7)  Lybrido
http://www.emotionalbrain.nl/lybrido (accessed Oct 30, 2014).

(8)  Lybridos
http://www.emotionalbrain.nl/lybridos (accessed Oct 30, 2014).

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Strong, K. (2014). Can Neuroscience Validate the Excuse “Not Tonight, Dear, I have a Headache?" The Neuroethics Blog. Retrieved on

, from http://www.theneuroethicsblog.com/2014/11/can-neuroscience-validate-excuse-not.html