Transcript 06 Hormonal Mechanismsx

06. Hormonal Control of
Behavior
Control of Behavior
• Neural Mechanisms
– Electrical impulses
– Direct connections
• Hormonal Mechanisms
– Chemical signals
– Distance connections
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Hormones
• What are they?
• Where are they made?
– What do they do?
• How do they differ from
neurological behavioral
controls?
• How do they control behavior?
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Hormones: What are they?
• Chemical substances
• Typically formed in specialized
groups of cells called glands
• Affect target cells in another
organ
– Target specific
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Hormones: What are they?
Can be:
Testosterone
• Steroids (lipids)
– Testosterone & Estrogen
• Proteins (peptides)
– Vasopressin
• Amines (small molecules)
– Epinepherine
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Hormones: Where are they made?
• Centrally
– Neurohormones
– Produces in the brain
– Travel to targets outside the
brain
– Hypothalamus
• Peripherally
– Endocrine glands
– E.g. adrenal and thyroid
glands
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Hormones: What do they do?
• Non-steroid hormones
– Cannot enter the cell
– Signaling pathways
• Steroid hormones
– Pass through the cell membrane
• Initiate Biochemical events
• Effects
– Physiological
– Neurochemical (behavioral)
– Cellular activity (gene regulation)
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Hormone based communication
• Intracrine
– Regulation of intracellular
events
• Autocrine
– Signaling feedback
influences cell that secreted
hormone
• Paracrine
– Affect adjacent/nearby cells
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Hormone based communication
• Endocrine
– Secreted into bloodstream
• Ectocrine
– Extracellular substances
such as pheromones
– Release into the
environment to
communicate with others
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Endocrine
• Ductless glands
• Rich blood
supply
– Products
secreted into
bloodstream
– Can travel to any
cell in the body
– Signal a response
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Ectocrine
• Release outside of the body
• Warning of Environmental danger to other
organisms
• Declaration of an individuals
state
– Injured
– Reproductive
– Dominant
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Hormones vs. Neurological controls
• Nerve impulses are fast
– Used for immediate
response to stimuli
• Hormonal signals are
slow (by comparison)
– Used for prolonged
responses
– Minutes, hours, days,
months
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Hormones vs. Neurological controls
• Hormones are able to
“prime” the system for
neurological impulses
• Changes in hormones
can cause changes in
neurological response
• COMPLEMENTRY
SYSTEMS
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How we study Hormones
• Ablation
– Removal of the gland
• Replacement
• Block receptors
• Measurement of circulating levels
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How do Hormones affect Behavior
• Nervous system
– Activational effects
• Sensory Perception
• Effector systems
• Development
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Nervous system
• Anatomy
– Can alter neurological
connections
• Impulse transmission
– Induce/inhibit receptors
• Biochemistry
– Stimulate neurorecptors
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Nervous system
Example
• Reflect reactions are accelerated by
epinepherine (adrenaline)
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Nervous system
Example
• Androgen in male
mice
– Castrated; do not
produce androgen
– Reduced sexual and
aggressive behavior
– Androgen implant
causes rescue of
behavior
• Vary placement of Androgen
supplement in the brain leads
to different behaviors
expressed
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In the Brain
• Influence Neuronal
responsiveness
• Gene activity
– Altering neuron
biochemistry
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Activational effects
• Relative turning on/off of a behavior
• Associated pattern
– Activity aligned with maximum hormone levels
• Dissociated pattern
– Activity aligned with minimum hormone levels
• Constant pattern
– Activity unchanging with hormone levels
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Activational effects
• Oxytocin
– Maternal behavior in mice
– Oxytocin injection induce maternal behavior
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Associated/Disassociated effects
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Sensory Perception
• Alter response to stimuli
– Sensitivity
– Behavior
Example
• Increased estradiol
production cause female
rats to be more responsive
to tactile cues
• Induce copulatory
behavior (lordosis)
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Sensory Perception
Example
• Salinity tolerance in oceanic stickleback
– Anadramous stickleback move into freshwater to
breed
– Hormones involved in salinity tolerance
(osmoregulation)
• Reproductive behavior
– Cortisol induces males to become parental
– Aggressive towards red coloration
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Effector System
• Modification of motor control
– Including structures
Example:
• Muscle
hypertrophy in
male frogs
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Effector System
• Seretonin primes flexor
muscles
– Escape response
– Octopomine inhibits flexor
response
• Prolactin induces tail fin
growth in male newts
– Reproductively favored
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Effector Systems
• Secondary sex traits in birds
Example: American Goldfinch
• Non-breeding season
– Drab male, no response to
female stimuli
• Breeding season
– Bright Male, respond to female
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Effector Systems
• Secondary sex traits in birds
• Female response to male color
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Development
• Affects the formation of features
– During critical period of pre/post-natal development
– Form before adulthood
Example:
• Testosterone supplement in 4 day old female rats
– Suppress sexual behavior as adults
• Estrogen supplement in 4 day old male rats
– Suppress sexual behavior as adults
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Development
• Endocrine disruptors
– Estrogen in water a feminizing agent
– Androgen a virilizing agent
• Malformed limbs
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Hormones & Behavior
Hormones can directly
influence behavior
• Individual genotypes
• Seasonal variations
• Experience
• Ecological influence
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Individual variation
• Production of
hormones can vary
due to genes
– Cause variation in
phenotype
• Male coloration in
lizards
– Tactic switching
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Seasonal variation
• Rely on seasonal cues
– Photoperiod
• But can persist in absence
of cues (internal clock)
Example
• Testosterone spike in Red
Deer cause spring rutting
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Seasonal Variation
• Testosterone in Male red
deer
– Testosterone spike mid
winter
– Stags become aggressive in
Early spring (Rut) sexually
active
– Castrated males show no
aggressive or mating
behavior
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Experience
• Experience can cause a
behavior to continue
– Even after hormonal stimulus is
gone (change in hormonal state)
Example
• Male house cats fixed before becoming sexually
mature do not display mating behavior
• Males fixed after at least 1 mating opportunity
– Continue to display copulatory behaviors
– Frequency and intensity decrease over time
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Experience
• Can also be bi-directional
– Social environment can affect
• Can also be bi-directional
– Social environment can affect
• Example: Spider monkeys
– Testosterone before establishing dominance hierarchy,
no effect on dominance
– After Rank, dominant male has highest levels
– If females present disparity in testosterone levels is
greater
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Long term controls
• Bio Rhythms
• Nervous system & hormones work together
– Short term responses (daily cycle)
– Long term (seasonal)
• Cyclical influences
– Light cycle
– Moon & Tidal cycle
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Sex Hormones
• Not truly sex-linked
– Males produce estrogen and progestrone
– Females produce androgen
• Circulating levels of corticosteroids control sex
• Cause by cell signals in the gonads
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Sex Hormones
• One enzymatic change can cause the switch from
Testosterone to estradiol
– And back
• Secondary regulatory mechanism
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Sexual Behavior
• Estrodiol and female mice
– Removal of ovaries causes
reduction in estrodiol
– Eliminates sexual behavior
(lordosis)
Estradiol
– Can be restored with
Estrodiol/Progesterone
replacement
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Sexual Behavior
• Androgen and male mice
– Castration reduces
androgen levels
– Diminishes sexual
behaviors (aggression,
copluatory activity)
– Androgen implant
recovers these activities
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How might behavior
affect hormones
• Behavior often does
affects hormone levels
– which in turn can
influence subsequent
behavior.
• World Cup Soccer Fans
were assayed for
testosterone before and
after the Brazil-Italy
final.
little Dutch football fan
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How might behavior
affect hormones
• Brazil won on penalty
kicks.
• 11/12 Brazil fans
showed an increase in
testosterone
little Dutch football fan
• 9 of 9 Italian fans
showed a decrease.
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How might behavior affect
hormones
• Testosterone concentrations
were measured in four
heterosexual couples over a
total of 22 evenings.
• On 11 evenings, saliva
samples were obtained before
and after sex
– On the remaining 11 evening,
two samples were obtained, but
there was no sex.
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How might behavior affect
hormones
• Having sex caused an increase in
testosterone in both men and
women.
– No changes were seen in the no-sex
nights.
• The early evening samples (revealed
no difference in testosterone
concentrations between sex and nosex evenings
– Suggesting that sex increases
testosterone more than testosterone
(concentrations) cause sex.
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How might behavior affect
hormones
• Alternatively, physical exercise may have
caused the increase
– It increases CORT, which can correlate positively
with Testosterone.
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