Hormones and Behavior
description
Transcript of Hormones and Behavior
![Page 1: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/1.jpg)
Hormones and Behavior
Alison Bell
Animal Biology
University of Illinois
![Page 2: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/2.jpg)
Today’s lecture
• Hormones– 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
![Page 3: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/3.jpg)
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.
![Page 4: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/4.jpg)
Hormones: What are they?
Chemically, they can be:– Lipids (e.g. steroids such
as testosterone)– Peptides/proteins (e.g.
vasopressin)– Amines/other small
molecules (e.g. epinephrine)
Testosterone
![Page 5: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/5.jpg)
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
![Page 6: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/6.jpg)
Hormones: What do they do?
• 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
Nonsteroid hormones: can’t enter cell Steroid hormones: pass right through
![Page 7: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/7.jpg)
Hormone regulation:Important vertebrate pathways
Hypothalamus-pituitary-gonad (HPG) Hypothalamus-pituitary-adrenal (HPA)
![Page 8: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/8.jpg)
Hormone regulation:Synthesis and metabolism
Bells and whistles:
Receptors
Plasma binding proteins
Enzymes
![Page 9: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/9.jpg)
How to study hormones?
•Remove the gland
•Add hormone
•Measure circulating levels
•Block receptor
![Page 10: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/10.jpg)
Sexual Behavior: Females
• Estradiol and mice– OVX mice: eliminates
female sexual behavior (lordosis)
– Can be restored by treatment with estradiol followed by progesterone Estradiol
![Page 11: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/11.jpg)
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
![Page 12: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/12.jpg)
Hormones BehaviorIf 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 femaleselect a nest site, marked by the female sitting on itbuild the nest – takes one weekcopulate during nest buildingfemale lays eggs, 2 eggs over 2 daysincubate the eggs – takes two weeksthe young hatch and the parents feed the young by producing a “crop milk” and regurgitating it for the young – takes two weeksinitiate sequence again
Role of progesterone…Lehrman 1964
![Page 13: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/13.jpg)
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
![Page 14: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/14.jpg)
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
![Page 15: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/15.jpg)
Activational Effect
• Oxytocin and maternal behavior in mice– Pre-maternal mice fear
pups and will attack them– Oxytocin injections induce
maternal behavior
![Page 16: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/16.jpg)
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
![Page 17: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/17.jpg)
Organizational EffectSexual 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
![Page 18: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/18.jpg)
Applying organization-activation theory to alternative phenotypes
The relative plasticity hypothesisAlternative 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
![Page 19: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/19.jpg)
The relative plasticity hypothesis
Moore et al 1998
![Page 20: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/20.jpg)
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
![Page 21: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/21.jpg)
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)
![Page 22: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/22.jpg)
Testosterone in male birds
![Page 23: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/23.jpg)
What explains the dynamics (change over time) of T?
![Page 24: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/24.jpg)
Costs of T
T
Level of behavior
Aggression
Parental behavior
![Page 25: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/25.jpg)
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
![Page 26: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/26.jpg)
Closer to home: hormones and human behavior
Undoubtedly, hormones involved in organizing and activating human sexual
behavior
What about unique human behaviors?
![Page 27: Hormones and Behavior](https://reader035.fdocuments.in/reader035/viewer/2022062410/5681597e550346895dc6bdee/html5/thumbnails/27.jpg)
• 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
Testosterone and aggression