Chapter 17 Sex and the Brain

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Chapter 17 Sex and the Brain
http//alpha.cc.tut.fi/henri/brains.html
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I. Introduction to Reproductive System

• Review pp 548-560

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II. Voles

• A. Prairie voles (17.9)
• 1. Intense mating period
• 2. Permanent mate
• 3. Shared care of young

http//204.202.137.115/sections/science/DailyNews/
lovechem0212.html
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II. Voles

• B. Montane voles
• 1. Live singly
• 2. Promiscuis
• 3. Only female cares for young and only for
  minimal amount of time

http//www.science-frontiers.com/sf099/sf099b08.ht
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II. Voles

• C. Oxytocin and vasopressin (17.10color)
• 1. Receptor distribution varies between voles
• cause-effect?
• http//exn.ca/news/images/19990208-eceptorbig.gif

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II. Voles

• C. Oxytocin and vasopressin
• 2. Female montane vole brain resembles prairie
  vole receptors during child rearing
• 3. When prairie voles mate
• a. incr vasopressin in males
• b. incr oxytocin in females

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II. Voles (prairie)

• C. Oxytocin and vasopressin
• 4. If vasopressin antagonist given just before
  mating, male does not form a long term
  relationship
• 5. If male is given vasopressin when first
  exposed to a female, he forms a strong preference
  for her
• 6. Similarly, oxytocin is necessary for
  females to form long term relationship

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II. Voles (prairie)

• C. Oxytocin and vasopressin
• 7. During child rearing
• a. vasopressin incr males fathering role
• b. oxytocin incr females mothering role
• 8. Giving vasopressin or oxytocin to montane
  voles does not affect behavior
• a. perhaps receptors not present or
  distribution is different
• cause-effect?

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II. Sexual Dimorphisms

• A. Controvery (human brains)
• 1. Measurement techniques (17.12)
• 2. Sampling
• 3. Significance
• 4. Individual variation
• 5. Replication
• 6. Nature vs. nurture
• SDN male 5x vs. female

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II. Sexual Dimorphisms

• B. Sex Hormones / Steroids and the Brain
• 1. Membrane bound responses
• a. rapid
• b. effects
• 1) membrane potential
• 2) transmitter receptor
• 3) transmitter release

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II. Sexual Dimorphisms

• B. Sex Hormones / Steroids and the Brain
• 2. Intracytoplasmic receptors
• a. slower change
• b. longer lasting change
• c. e.g., promote/inhibit transcription
• d. analagous to NT receptors

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II. Sexual Dimorphisms

• B. Sex Hormones / Steroids and the Brain
• 3. Effects of age
• a. organizational effects
• 1) during development
• 2) long term
• 3) trigger development of male/female
  gonads
• 4) brain areas (?)

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II. Sexual Dimorphisms

• B. Sex Hormones / Steroids and the Brain
• b. activational effects
• 1) after development/puberty
• 2) temporary
• 3) triggers behavior
• c. nature vs. nurture

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II. Sexual Dimorphisms

• B. Sex Hormones / Steroids and the Brain
• 4. Estrogen and excitability
• a. female rats hippocampal dendritic
  spines cycle with estrous cycle (plasticity)
• b. directly proportional (17.15)
• c. control maintain low estrogen,
  administer estrogen, count spines

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II. Sexual Dimorphisms
Rat

• B. Sex Hormones / Steroids and the Brain
• d. hippocampus more excitable with incr
  dendritic spines (17.16)
• e. incr spines directly proportional with
  excitatory synapses
• f. incr spines directly proportional with
  incr NMDA receptors (excitatory)

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II. Sexual Dimorphisms

• B. Sex Hormones / Steroids and the Brain
• g. mechanism (?)
• 1) estradiol receptor in inhibitory
  neurons
• 2) estradiol causes decr GABA
• 3) causes decr inhibition
• 4) causes incr neuronal activity
• 5) somehow causes incr dendritic spines
  Hebbian synapses?, plasticity?

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II. Sexual Dimorphisms

• B. Sex Hormones / Steroids and the Brain
• h. epilepsy
• 1) females with certain forms of
  epilepsy are more likely to have seizures during
  stage of menstrual ccle with highest ratio of
  estrogen/progesterone
• 2) video-Sandy Craddock violence and
  menstrual cycle, epilepsy and violence. 4min

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II. Sexual Dimorphisms

• C. Sexual Orientation (S. LeVay)
• 1. Interstitial nucleus of the anterior
  hypothalamus (INAH)
• a. INAH-3 2x males vs females
• b. INAH-3 gay males vs females
• c. INAH-3 2x straight males vs gay males
  (17.17)
• Simon LeVay 1991

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II. Sexual Dimorphisms

• C. Sexual Orientation
• 2. Nature vs nurture (is dimorphism present
  during development?)
• 3. Twin studies show lt 100 share sexual
  orientation
• 4. Few replications
• 5. Sampling?
• Related to Dorner study (stress?homosexuality)
  ?

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Think About

• Brain
• Body