Hormones and Behavior 1

10/31/2011
HORMONES AND BEHAVIOR
BEHAVIOR
• What animals do
– Mating
– Feeding
– Communicating
– Escaping predators
– Migration and dispersal
HORMONES
• Biological signal molecules
– Secreted into blood
– Carried to target tissues
– Affect diverse processes
•
•
•
•
Growth
Development
Physiology
Behavior
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HORMONES and BEHAVIOR
• Also known as “behavioral endocrinology”
– Integrative field
• Effects of hormones on behavior
• Effects of behavior on hormones
• Importance of mechanisms in evolution
– Regulation of life history variation
HISTORICAL ROOTS
• Castration of domesticated animals for at least
2000 years
– Produces capons, steers, geldings, etc
– Removes primary source of testosterone
– Affects quality as food
– Affects behavior
• More manageable
• Less disruptive socially (less interested in sex, fighting)
HISTORICAL ROOTS
• Castration of humans
– Castrati and Eunuchs: Prepubertal castration
• Castrati: Castration intended to retain singing voice
• Eunuchs: Castration intended to eliminate sex drive
– Employed as guards for women (including harems)
– Timing of castration important
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BERTHOLD’S EXPERIMENT
• 1849: A. A. Berthold
performed first formal
endocrinology
experiment
• Demonstrated nonneural contribution by
the testes required for
normal development
of a rooster
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BERTHOLD’S EXPERIMENT
CONCLUSIONS
• Transplanted testes fully functional
• Birds with transplanted testes entirely normal
– Normal appearance
• Combs,
C b wattles,
ttl
plumage
l
– Normal behavior
• Normal vocalizing
• Normal aggression
• Normal mating
BERTHOLD’S EXPERIMENT
CONCLUSIONS
• Hypothesized secretory product carried by blood
to target tissues
– Learned later to be testosterone
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HORMONES
• Organic molecules produced and released into
blood by endocrine (ductless) glands and
tissues
• Carried by blood to target tissues
• One or more examples produced by virtually all
tissues
HORMONES
• Generally play dual roles coordinating behavior
and physiology
– Example: Same hormones regulate gamete
maturation and mating behavior
• Mature gametes available when animals most actively
engaging in reproductive behavior
– (Some exceptions)
HORMONES vs
NEUROTRANSMITTERS
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HORMONE SPECIFICITY
• Specific hormones only affect certain cells
• Hormones affect different cells in different ways
– Target cells possess receptors for specific hormones
– Target
T
t cells
ll vary in
i th
the ttransduction
d ti machinery
hi
th
they
possess
– Diverse responses to particular hormones possible
TINBERGEN’S “4 QUESTIONS”
ABOUT BEHAVIOR
•
•
•
•
How does it develop?
What mechanisms cause it?
How did it evolve?
How does it contribute to
survival?
Niko
Tinbergen
LEVELS OF ANALYSIS
• PROXIMATE CAUSES
– Developmental mechanisms
• Genetic determinants of behavior
• Environmental determinants of behavior
– Immediate causal mechanisms
• Systems for detection of environmental stimuli
• Systems for integrating and adjusting responsivenes to
stimuli
• Systems for carrying out responses
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LEVELS OF ANALYSIS
• ULTIMATE CAUSES
– Historical pathways leading to behavioral trait
• Evolutionary stages, from origin of trait to present
– Effects of selection on history of trait
• Effects of past and current usefulness on survival and
reproductive success
– Both natural and sexual selection important
HORMONE – BEHAVIOR
INTERACTIONS
HORMONE – BEHAVIOR
INTERACTIONS
• Proximate
– Hormones affect development and expression of
behavior
• Do not cause behavior themselves
• Affect frequency and intensity of expression
• Organizational / activational effects
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HORMONE – BEHAVIOR
INTERACTIONS
• Ultimate
– Mechanistic control of behavior affects fitness
– Mechanisms shared by related taxa
– Affects evolution of both behavior and mechanisms
underlying development and expression of it
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Overview of the Endocrine System
I. The endocrine system: general considerations
Definitions
Classes of hormones
VI. Gonads Male& Female
Vertebrate endocrine glands
Androgens
Progesterone
II. Hypothalamus/pituitary
Estrogens
Anatomy
Anterior pituitary hormones
Posterior pituitary hormones
VII Digestive system
VII.
Hypothalamic releasing hormones
Pancreas
Stomach/small intestine
III. Pineal gland
Melatonin
VIII. Mechanisms of hormone action
General considerations
IV. Thyroid gland
Hydrophilic hormones
Thyroid hormone
(Peptides/amines)
Lipophilic Hormones
V. Adrenal gland
(Steroid hormones/
Catecholamines
thyroid hormones)
Adrenal steroids
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WHAT EXACTLY ARE HORMONES?
• Organic molecules produced and released into blood by
endocrine (ductless) glands and tissues
• Carried by blood to target tissues
• Specific hormones only affect certain cells and hormones affect
different cells in different ways
– Target cells possess receptors for specific hormones
– Target cells vary in the transduction machinery they possess
– Diverse responses to particular hormones possible
• Effects are typically slower and longer lasting than effects of the
nervous system
Various intercellular signaling strategies
As opposed to:
Nelson Fig. 2-1
THE NERVOUS SYSTEM AND THE ENDOCRINE SYSTEM ARE HIGHLY INTEGRATED!
How do hormones influence the nervous system?
Neurogenesis (new neurons)
Apoptosis (death of neurons)
Synaptogenesis (new synapses)
Neuritogenesis (new inputs)
Conduction velocity
Alter membrane potential
Thus, hormones can act as “neuromodulators”
How does the nervous system influence endocrine system?
Neurons secrete hormones (“neurohormones”)
Neurons induce endocrine glands to secrete hormones
Neurons alter target cell sensitivity
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Classes of hormones
1.Steroid hormones:
Derived from series of enzymatic modifications of cholesterol
Androgens like testosterone, estrogens like estradiol, progestins like
progesterone (androgens, estrogens, and progestins are sometimes
referred to as “sex steroid hormones”)
Also, glucocorticoids like cortisol or corticosterone and
mineralocorticoids like aldosterone, etc.
2. Fatty acid derivatives (prostaglandins)
Classes of hormones, continued
3. Amino acid derivatives
Thyroid hormone (coupling of two iodinated tyrosines)
Amines: Epinephrine and Norepinephrine, Melatonin
and Dopamine
4. Peptide hormones
Size range: 3 amino acids (thyrotropin releasing hormone)
to about 200 amino acids (e
(e.g.
g prolactin
prolactin, growth hormone)
-produced by transcription of a hormone gene, translation of
mRNA, proteolytic processing and other enzymatic
modifications to produce mature peptide hormone
Major vertebrate endocrine glands
Endocrine glands:
Ductless
Rich blood supply
Secrete chemical messengers (hormones) into bloodstream
Hormones affect only cells that have appropriate receptors
Nelson Fig. 2-3
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Two key components of endocrine system:
The Hypothalamus and Pituitary
Hypothalamus organized into “nuclei”
-clusters of neuronal cell bodies
Nelson 2-4
Intermediate pituitary
Hormones of the
posterior pituitary
(both also produced in
discrete brain regions)
1.
Arginine vasopressin (AVP)
Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH2
or Arginine vasotocin (AVT):nonmammals
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Arg-Gly-NH2
Physiological roles: fluid balance and blood
pressure
Behavioral roles too (pair bonding)
2. Oxytocin or related peptides
2
Physiological roles:
Smooth muscle contraction mammary gland,
uterus, male reproductive tracts
Behavioral roles too (pair bonding)
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2
To general circulation
Nelson 2-6
Hormones of the anterior pituitary
(all peptide hormones)
Gonadotropins:
(in median
eminence)
Luteinizing hormone (LH)
Testosterone synthesis
Induce ovulation
Follicle stimulating hormone (FSH)
Gamete maturation
Estrogen synthesis
Thyroid stimulating hormone (TSH)
Thyroid gland growth
Thyroid hormone synthesis
All are glycoproteins and share a common alpha subunit
but have different beta subunits that confer specificity
To general circulation
Nelson 2-6
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Hormones of the anterior pituitary, continued:
Pro-opiomelanocortin (POMC) gives rise to:
1. Adrenocorticotropic hormone (ACTH)
-Glucocorticoid synthesis by
adrenal cortex
-Behavioral effects too
(learning/memory and food
uptake)
Anterior pit.
Intermediate
pit.
{
ACTH
ACTH
{ MSH
CLIP
LPH
LPH
END
LPH
END
Simplified from Nelson 2-22
2. LPH, CLIP: ??
3. Melanocyte stimulating hormone
(MSH): coat, skin color (not in
Humans)
Endorphin (END):
Endogenous opioids, pain modulator
Note: ACTH and endorphin produced in
discrete brain regions as well
Hormones of the anterior pituitary, continued:
Growth hormone (GH)
Somatic cell growth/ bone growth via
insulin-like growth factor secretion
Metabolic effects (glucose, amino acids)
Prolactin (PRL)
Lactation (mammals)
Crop milk production (some birds)
Nutritious secretions (some fish)
Incubation patch edema (birds)
Freshwater adaptation (migrating fish)
Behavioral effects too
Parental care in multiple vertebrate species
Water drive (salamanders)
Hypothalamic releasing or inhibiting hormones
(All peptide hormones except dopamine-made directly from
tyrosine)
Gonadotropin releasing hormone (GnRH)
-induces gonadotropin secretion (LH and FSH)
Gonadotropin inhibiting hormone (GnIH)
-the opposite (and other things)
Thyrotropin releasing hormone (TRH)
induces TSH secretion
-induces
Corticotropin releasing hormone (CRH)
-induces ACTH secretion
Somatostatin-inhibits GH secretion
Growth hormone releasing hormone (GHRH)
-induces GH secretion
Prolactin inhibiting hormone (PIH): Most likely dopamine
-inhibits PRL secretion
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The pineal gland
Secretes melatonin in absence of light
Inhibits reproductive axis in seasonally breeding mammals
Influences sleep/wake cycle
(from tryptophan)
Nelson 2-10
The thyroid gland
80%
Follicle
TSH
(from
Anterior
Pit.)
Target tissues
20%
Nelson 2-7
The adrenal glands
Aldosterone
(Angiotensin II+)
Cortisol
OR
(ACTH+)
Corticosterone
OR
AND
Adrenal androgens
(ACTH+)
Sympathetic
input
Epinephrine
Norepinephrine
(from tyrosine)
Nelson 2-9
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Sex steroid biosynthesis in the gonads
Progesterone
Pregnenolone
Androgens
5 reductase
Dihydrotestosterone (DHT)
Aromatase
Estrogens
11- ketotestosterone (11-KT)
(Important androgen in many fish)
Nonaromatizable to estrogens
http://www.physci.ucla.edu/research/schlinger/kiranDHEA.html
Male gonads: testes
FSH
LH
Peripheral tissues,
Testosterone
brain
Nelson Fig. 2-11
Female gonad: ovaries
LH
FSH
Testosterone
FSH
Estradiol
LH
Nelson Fig. 2-12
Peripheral tissues,
brain
Estradiol
Progesterone
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Other endocrine glands/tissues of note
Parathyroid glands: Parathyroid hormone (calcium balance)
Pancreas: Insulin (decrease blood glucose)
Glucagon (increase blood glucose)
Skin: Vitamin D (calcium balance)
Stomach/Duodenum: Secretin (neutralize acid from stomach)
Cholecystokinin (induce pancreatic
enzymes bile secretion)
enzymes,
Gastrin (Stomach secretions)
Multiple other peptides implicated
nutrient digestion/absorption and
in feeding behaviors
White adipose tissue: Leptin (decrease feeding)
Feedback loops often control hormone synthesis
Nelson Fig. 2-36
HOW DO HORMONES WORK?
Part I: Hydrophilic (Water soluble) Hormones use
membrane receptors: Amines, peptide hormones
Activate 2nd messenger cascades
Gets signal across membrane
Amplifies hormonal signal
C
Cross-regulation
l ti with
ith other
th signals
i
l
Can change cell function without new protein synthesis
Cell shape, movement, ion channel activity,
secretion, enzyme activity
Can also change cell function via new protein synthesis
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A very common membrane receptor type: G-protein coupled receptor
Peptides
Etc.
Cell membrane
Bockaert and Pin, 1999
G protein coupled receptors: cAMP as second messenger
Adenylate
cyclase
 subunit of G protein
exchanges GDP for GTP,
activates adenylate cyclase
Also ion channels,
transcription factors, etc.
MODIFIED from Nelson 2-16
G protein coupled receptors: Calcium as second messenger
Protein
kinase C
Phospholipase C
is activated by GTP bound
G protein  subunit
Substrate
phosphorylation
Additional
kinase activation
MODIFIED from Nelson 2-17
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Diversity of effects from same hormone: AVP as an example
V2R
V1aR
V1bR (or V3)
AVP
AVP
G
Gs
Activate Adenylate
cyclase cAMP
G
Gq
Activate Phospholipase
C IP3 and Ca2+
Water reabsorption
in kidney
Vascular smooth
muscle contraction
Gq
Activate Phospholipase
C IP3 and Ca2+
Modulate ACTH release
Behavioral effects
(Pair bonding)
Part II: Lipophilic, or fat soluble, hormones (steroid hormones and thyroid hormones)
primarily use intracellular receptors, also known as nuclear receptors
GENERALLY slower acting, and have longer lasting effects than
hydrophilic hormones
i.e. Cortisol (a lipophilic steroid hormone)- chronic stress response leads
to elevated blood glucose levels from increased gluconeogenesis, and
increase blood amino acid levels from muscle and connective tissue
protein breakdown (to combat starvation)
Contrast with a hydrophilic hormone:
Epinephrine (bioamine, works via G protein-coupled membrane receptor)
-acute stress response leads to reinforcement of sympathetic output
(elevated heart rate, blood pressure) as well as rapid elevation of
blood glucose levels
Intracellular (nuclear) receptor function
?
?
Cytoplasm
Ribosomes
No hormone
R
Nucleus
R
Target gene
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Intracellular (nuclear) receptor function
?
?
Cytoplasm
e.g. Estradiol
2nd messengers etc.
AAA
New mRNA
Nucleus
New protein
Best known
pathway
R
R
Target gene
Receptor Specificity examples
Ligands (in order of potency)
Nuclear receptor
17  estradiol=Diethylstilbestrol (DES)
>estrone
Estrogen receptor (ER)
DHT=11- ketotestosterone
>testosterone>>DHEA
Androgen receptor (AR)
Progesterone
Progesterone receptor
((PR))
Glucocorticoid receptor
(GR)
Mineralocorticoid receptor
(MR)
Thyroid hormone receptor
(TR)
Cortisol=corticosterone>>cortisone
Aldosterone
Triiodothyronine>Thyroxine
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