06 Hormonal Control of Behavior Control of Behavior

06. Hormonal Control of Behavior

Control of Behavior • Neural Mechanisms – Electrical impulses – Direct connections • Hormonal Mechanisms – Chemical signals – Distance connections 2

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? 3

Hormones: What are they? • Chemical substances • Typically formed in specialized groups of cells called glands • Affect target cells in another organ – Target specific 4

Hormones: What are they? Can be: Testosterone • Steroids (lipids) – Testosterone & Estrogen • Proteins (peptides) – Vasopressin • Amines (small molecules) – Epinepherine 5

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 6

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) 7

Hormone based communication • Intracrine – Regulation of intracellular events • Autocrine – Signaling feedback influences cell that secreted hormone • Paracrine – Affect adjacent/nearby cells 8

Hormone based communication • Endocrine – Secreted into bloodstream • Ectocrine – Extracellular substances such as pheromones – Release into the environment to communicate with others 9

Endocrine • Ductless glands • Rich blood supply – Products secreted into bloodstream – Can travel to any cell in the body – Signal a response 10

Ectocrine • Release outside of the body • Warning of Environmental danger to other organisms • Declaration of an individuals state – Injured – Reproductive – Dominant 11

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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 13

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 14

How we study Hormones • Ablation – Removal of the gland • Replacement • Block receptors • Measurement of circulating levels 15

How do Hormones affect Behavior • Nervous system – Activational effects • Sensory Perception • Effector systems • Development 16

Nervous system • Anatomy – Can alter neurological connections • Impulse transmission – Induce/inhibit receptors • Biochemistry – Stimulate neurorecptors 17

Nervous system Example • Reflect reactions are accelerated by epinepherine (adrenaline) 18

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 19

In the Brain • Influence Neuronal responsiveness • Gene activity – Altering neuron biochemistry 20

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 21

Activational effects • Oxytocin – Maternal behavior in mice – Oxytocin injection induce maternal behavior 22

Associated/Disassociated effects 23

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) 24

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 25

Effector System • Modification of motor control – Including structures Example: • Muscle hypertrophy in male frogs 26

Effector System • Seretonin primes flexor muscles – Escape response – Octopomine inhibits flexor response • Prolactin induces tail fin growth in male newts – Reproductively favored 27

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 28

Effector Systems • Secondary sex traits in birds • Female response to male color 29

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 30

Development • Endocrine disruptors – Estrogen in water a feminizing agent – Androgen a virilizing agent • Malformed limbs 31

Hormones & Behavior Hormones can directly influence behavior • Individual genotypes • Seasonal variations • Experience • Ecological influence 32

Individual variation • Production of hormones can vary due to genes – Cause variation in phenotype • Male coloration in lizards – Tactic switching 33

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 34

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 35

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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 37

Experience • 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 38

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 39

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 40

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Sex Hormones • One enzymatic change can cause the switch from Testosterone to estradiol – And back • Secondary regulatory mechanism 42

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 43

Sexual Behavior • Androgen and male mice – Castration reduces androgen levels – Diminishes sexual behaviors (aggression, copluatory activity) – Androgen implant recovers these activities 44

How might behavior affect hormones • Behavior often does affects hormone levels – which in turn can influence subsequent behavior. little Dutch football fan • World Cup Soccer Fans were assayed for testosterone before and after the Brazil-Italy final. 45

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. 46

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. 47

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. 48

How might behavior affect hormones • Alternatively, physical exercise may have caused the increase – It increases CORT, which can correlate positively with Testosterone. 49

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