1. Alison Bell Animal Biology University of Illinois
Hormones and Behavior
Alison Bell
Animal Biology
University of Illinois

2. Today’s lecture Hormones Hormones and behavior What are they?
Where are they made?
What do they do?
Hormones and behavior
Organization-activation
Relative plasticity hypothesis
In utero and parental effects
Challenge hypothesis

3. Hormones: What are they?
Chemical substances, formed in a specialized gland or group of cells, released into the blood that affect target cells in another organ.
Distinct from:
Neurotransmitters, substances released by neurons that are received by adjacent neurons & alter their membrane potential.
Pheromones, substances released by an individual as scent signals for another.

4. Hormones: What are they?
Testosterone
Chemically, they can be:
Lipids (e.g. steroids such as testosterone)
Peptides/proteins (e.g. vasopressin)
Amines/other small molecules (e.g. epinephrine)

5. Hormones: Where are they made?
Peripherally
Endocrine glands, e.g. adrenal gland, thyroid gland
Gonads, e.g. testes, ovaries
Centrally
‘Neurohormones’ are produced within the brain, but travel to target via bloodstream
e.g. hypothalamus, neurosteroidogenic cells

6. Hormones: What do they do?
Nonsteroid hormones: can’t enter cell
Steroid hormones: pass right through
Many physiological effects: regulation of reproduction, growth, osmotic balance, heart rate, etc.
In the brain: influence neuronal responsiveness, or activity of certain genes within the neuron, thus altering the biochemistry of the brain to alter behavior

7. Hormone regulation: Important vertebrate pathways
Hypothalamus-pituitary-gonad (HPG)
Hypothalamus-pituitary-adrenal (HPA)

8. Hormone regulation: Synthesis and metabolism
Bells and whistles:
Receptors
Plasma binding proteins
Enzymes

9. How to study hormones? Remove the gland Add hormone
Measure circulating levels
Block receptor

10. Sexual Behavior: Females
Estradiol and mice
OVX mice: eliminates female sexual behavior (lordosis)
Can be restored by treatment with estradiol followed by progesterone
Estradiol

11. Sexual Behavior: Males
Red deer stag
Sept/Oct become aggressive, begin courting females
Testes generate sperm and release testosterone
Castrated males do not fight or mate
Testosterone implants restore behavior

12. Hormones
Behavior
If a male and female ring dove are placed in a cage containing a bowl and nesting material, and kept in simulated spring, they will initiate the following sequence:
bow and coo display, where the male bows and coos to the female
select a nest site, marked by the female sitting on it
build the nest – takes one week
copulate during nest building
female lays eggs, 2 eggs over 2 days
incubate the eggs – takes two weeks
the young hatch and the parents feed the young by producing a “crop milk” and regurgitating it for the young – takes two weeks
initiate sequence again
Role of progesterone…
Lehrman 1964

13. Important point
Many shared mechanisms, BUT mechanisms often differ between species/groups
Different selection pressures result in modifications of the hormonal mechanisms of behavior
Hunt et al 1995

14. Modes of Hormone Action
Activational effects
Short-term, reversible effects that occur in the fully developed organism (e.g. alteration of transmission in neural networks that respond to certain aspects of the environment)
Organizational effects
Long-term, irreversible effects on tissue differentiation and development (e.g. brain, ovary) that can either directly (brain) or indirectly (ovary) influence behavior
Critical or sensitive period

15. Activational Effect Oxytocin and maternal behavior in mice
Pre-maternal mice fear pups and will attack them
Oxytocin injections induce maternal behavior

16. Another activational example
Oxytocin and maternal behavior in sheep
Stimulation of birth canal during parturition results in oxytocin release in brain
Oxytocin injections cause non-pregnant females to accept alien lambs in 30 seconds!
Dolly the sheep and her surrogate mom

17. Organizational Effect
Sexual differentiation via exposure to steroids during development
Figure 1. Sexual dimorphisms in the brain.
(a,b) The sexually dimorphic nucleus of the preoptic area (SDN-POA) is larger in male rats (a) than in females (b) because the testes secrete testosterone during the perinatal sensitive period. After that time, testosterone has little effect on SDN-POA volume. (c,d) In contrast, the volume of the rat posterodorsal medial amygdala (MePD), which is about 1.5 times larger in males (c) than in females (d), retains its responsiveness to testosterone throughout life. (e,f) In zebra finches, the robustus archistriatum (RA) nucleus is crucial for song production and has a greater volume in males (e) than in females (f). Like the rat SDN-POA, exposure to steroid hormones early in life is essential for the RA to develop a masculine phenotype. For the RA, however, the steroids may not originate from the testes, but are rather synthesized locally in the brain itself. SCN, suprachiasmatic nucleus; 3V, third ventricle; ot, optic tract. All scale bars = 250 mum. Morris et al 2004

18. Applying organization-activation theory to alternative phenotypes
The relative plasticity hypothesis
Alternative phenotypes – within-sex variation in phenotype (morphology, behavior), e.g. sneakers vs territorial males
Fixed: individual permanently, irreversibly differentiated into one or the other type and doesn’t change phenotype during lifetime, e.g. satellite vs territorial ruffs, hooknose or jack salmon
Plastic: individual can change phenotype, e.g. calling vs intercepting frogs depending on local conditions
Moore et al 1998

19. The relative plasticity hypothesis
Moore et al 1998

20. Effects of exposure to hormones on behavioral development
Mice and aggressiveness
Subtle differences in the hormonal environment during embryonic development influence adult behavior
E.g. Males: 2M more aggressive later on.
E.g. Females: 2M more aggressive (correlated with territory size as adults)
Vom Saal et al

21. Another interesting way in which developing embryos are exposed to hormones…
Gil et al 1999, zebra finches
Females mated to relatively attractive males deposited more testosterone in their eggs compared to females mated to unattractive males
The differential allocation hypothesis (Burley 1988)

22. Testosterone in male birds

23. What explains the dynamics (change over time) of T?

24. Costs of T
Aggression T
Parental behavior
Level of behavior

25. The challenge hypothesis
In species where males provide direct parental care (feed the chicks), males should increase T only when needed, e.g. when challenged, but then return T to level B. In contrast, in species where males do not provide direct parental care and spend most of their time defending the territory, males should have high, relatively unchanging, levels of T.
Wingfield et al 1990

26. Closer to home: hormones and human behavior
Undoubtedly, hormones involved in organizing and activating human sexual behavior
What about unique human behaviors?

27. Testosterone and aggression
Some studies find higher T in CSF of aggressive males
Meta-analysis of 45 studies: weak, positive correlation between T & aggressiveness
May be more related to “dominance”
Serotonin may be more important in aggression
Ritualized aggression?
Men experience a surge in T after team/individual wins in sports
World Cup soccer fans show increased T if their team wins