Steven Crane Compiled Section Handouts. Human Behavioral Biology 2012

D2 receptors are on the post-synaptic neuron per usual

D1 receptors are pre-synaptic autoreceptors, the bookkeepers.

Receptor function

• D2 stimulation facilitates formation of a new pair bond

• D1 stimulation does the opposite: makes voles uninterested in forming pair bonds

Plasticity

• D2 receptors up-regulated in the dopamine circuit when voles are first mating. Forms the pair bond.

• After pair bonding, D1 receptors are up-regulated, so they aren't inclined to form new pair-bonds

What region is associated with long-term relationships and feelings of comfort, familiarity, needing?

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  The anterior cingulate
  

What's the role of the frontal cortex in sexual behavior? What NT does it tend to use?

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  Tends to use serotonin, but receives lots of dopamine projections.
  
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  Makes "the hard choice."
  
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    Could be inhibiting sexual impulses in inappropriate contexts.
    
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    Or could be fueling sexual impulses in cases where it's scary/difficult to do so.
    

What are the endocrine RESPONSES to sex?

How do hormones differ between genders in RESPONSE to sex?

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  Females:
  
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    Progesterone increase (reinforces pleasure, prepares for pregnancy)
    
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    Androgens increase (mediates sexual motivation)
    
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    Oxytocin increase (attachment, trust, mediate release of dopamine for pair bonds)
    
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  Males
  
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    Testosterone increase AFTER sex
    
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    Vasopressin increase – we see high levels of vasopressin receptors in meso-limbic dopamine system of pair-bonding species, which cause dopamine release (increasing monogamous behavior)
    
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      Ex. Change VP receptors in voles € can cause poly to be mono
      
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      Ex. Men with mono version more likely to marry and not divorce
      
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      Remember: this is the vasopressin receptor promoter that has the variation, not the receptor itself. So it's about expression patterns.
      
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      Take-home point (THP): express vasopressin receptors in the mesolimbic regions of the brain and the animal will be more likely to be monogamous.
      

What's the neurobiology of sexual orientation in males?

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  The INAH-3 (interstitial nucleus of the anterior hypothalamus) comes in different sizes.
  
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    Men have a 2x larger INAH-3 on average with huge variability and overlap compared to women.
    
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    One finding from Simon LeVay shows that gay men's INAH-3 is about halfway between the size of straight men and women. Has confounds because the gay men had died of AIDS.
    
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  Finger-length ratios and otoacoustic emission also show a gender difference with gay men, on average, between straight men and women.
  

And the nbio of sexual orientation in females?

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  "The literature here is smaller than for male sexual orientation. Some studies suggested elevated levels of androgenic hormones in lesbians versus straight women, some suggestions of elevated prenatal exposure to androgens. A few studies suggest that the 4th to 2nd finger ratio in lesbians differs from that of straight woman, in the direction more of the male average. Ditto for otoacoustic emission. There’s also some studies suggesting “male-like” cognitive profiles in terms of visuospatial tasks, verbal fluency. Of note, though, these are all very small effects, highly variable. A few studies have suggested that these patterns are more pronounced in lesbians who are self-described “butches” (i.e., women who take more stereotypically masculine roles during sex)." -from Extended Notes
  

And the nbio of transsexuality?

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  Note on defining gender/sex: can be done by chromosomes, gonads, hormones, external genitalia, secondary sexual characteristics, and/or psychosocial identity.
  
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  The BNST (bed nucleus of the stria terminalis) comes in different sizes.
  
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    Large sex difference in the size of a part of the BNST with a lot of predictive power
    
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    In transgender people (who feel their anatomical sex doesn't match their identity), the BNST tends to be the size of the sex they feel they should be rather than the one they are.
    
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    Conclusion: maybe less of a "psychological pathology" as it's been thought of; more a case of being stuck in the body of the wrong gender.
    
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  "Around 60% of men who have had their penises removed (because of penile cancer) have phantom penis sensations, whereas male-to-female transgendered individuals do not." -Extended notes