NSCI 201-Reproductive Behaviour

!!! edits made for hypothalamic regulation anterior pituitary, dopamine inhibits prolactin secretion !!!

hormones

• ductless glands with rich blood supply

• secreted into bloodstream

• travel throughout body

• bind to receptors

• coordinate multiple organs

• longer-lasting than neurotransmitters

4 classes of hormones

1. peptides or proteins (from several amino acids)

2. monoamines (from an amino acid)

3. lipid-based hormones (from a fatty acid)

4. steroids (from cholesterol)

examples of monoamines (class of hormones)

epinephrine, melatonin, dopamine

examples of steroids (a class of hormones)

androgens, estrogens, progestins, glucocorticords

two methods of hypothalamic control for pituitary function

1. peptide hormones released into the local blood system and regulate anterior pituitary (GnRH, CRH)

2. peptides directly released into posterior pituitary and secreted into general (systemic) blood system (oxytocin, arginine vasopressin)

what behavior does the preoptic area play an important role in

reproductive behavior

gonads

• testes and ovaries

• stimulate production of gametes

ductless

no connection between the organ and the blood, small molecules released and diffused

neurotransmitters vs hormones

neurotransmitter: local communication, very short

hormones: broad signals, long-distance messengers with long-lasting effects

hormones and the location of receptors

• peptide hormones: receptors in the transmembrane

• steroid hormones: receptors in and out of the cell

dopamine

• produced by adrenal gland in the bloodstream

• can act as both hormones and neurotransmitters

• no gene, made from amino acid

what important role does the hypothalamus play related to the pituitary glands

critical for regulating the endocrine system

two hormones released into the general blood supply

FSH, LH

portal system

“private little blood system”

plexus

branching network of capillaries

primary plexus in hypothalamus

• axons releasing hormones to primary plexus

• peptides travel down blood to secondary plexus

• communicate with cells in the pituitary

hormone release in posterior pituitary

• axons project directly (no portal system)

• oxytocin and vasopressin released into general circulation

leydig cells in testes

-in between the seminiferous tubule

-have all the enzymes to make testosterone from cholesterol

role of testosterone

important for cell maturation

testosterone and coordination of reproductive behavior

testosterone provides negative feedback to the thalamus → inhibits the production of GnRH → prevents an overshot

(this is a good way to sync gonads with behavior)

androgens

binds to androgen receptor, includes testosterone, androstenedione, DHT

thecal cells

have several layers and the enzymes that make androgen

aromatase

turns androgens into estrogens

ex. testosterone into estradiol (E2)

-crosses the plasma membrane

-present in the nerves of male and female

corpus luteum

yellow body, contains lots of fats and produces PROG and E2

estrogens

a class of molecules that bind to estrogen receptor

estradiol

a type of estrogen, aromatase turns testosterone into estradiol

follicular phase in female HPG axis

low FSH to ovary, high estradiol from ovary

ovulation phase in female HPG axis

estradiol switches to positive feedback, increase of FSH and LH from anterior pituitary which helps ovulation

GnRH regulates which hormones in the anterior pituitary, targets which organs?

LH and FSH

gonads (ovaries/testes)

effects of GnRH in females

follicle development, ovulation, E2 and PROG secretion

CRH regulates which hormones in the anterior pituitary, targets which organs?

ACTH

adrenal cortex

effect of CRH

glucocorticoid secretion

TRH regulates which hormones in the anterior pituitary, targets which organs?

TSH

thyroid gland

effect of TRH

thyroid hormone secretion

DA regulates which hormones in the anterior pituitary, targets which organs?

prolactin (inhibition)

mammary glands

effect of DA

milk production

GHRH regulates which hormones in the anterior pituitary, targets which organs?

growth hormone

body cells

effect of GHRH

growth

male hormones (why is the term misleading)

-male brain contains aromatase (enzyme that makes estrogens)

-local synthesis of E2 and PROG

-PROG in blood

females hormones (why is the term misleading)

-synthesize T in ovary, mainly as precursor to E2

-T and AE in blood

immunoassay

method of measuring a presence or concentration of molecule (hormones) using antibodies

-weakness in terms of specific binding

method:

add sample solution containing antigen → antigen is captured by antibody → add enzyme-labeled second antibody → second antibody binds to captured antigen → add chromogenic substrate of enzyme and estimate amount of antigen from absorbance

mass spectrometry

ions “fly” in magnetic fields:

goes through Q1 mass filter where magnetic field is produced → Q2 collision cell where fragmentation happens → Q3 mass filter for ion selection → detector measures ion abundance

-used for high specificity

transport and release of peptide/protein hormones

-soluble in blood (but have protection fro degradation)

-stored in vesicles and released in response to a stimulus

transport and release of lipid soluble hormones

-use carrier proteins to travel through blood

-not stored

peptide or protein hormone receptor

-governed by a single dna sequence

-receptors are regulated, taken in and out of membrane when necessary

intracellular steroid hormone receptors

1. in the cytoplasm or cell nucleus

2. regulate gene expression

3. slow acting (at least 30min)

4. enduring effects

membrane-bound steroid hormone receptors

1. in plasma membrane or outer mitochondrial membrane

2. regulate enzymes (kinases)

3. fast acting

4. temporary effects (no genomic effects)

hormone response element (HRE)

-intracellular steroid receptors

-located where ligand/receptor complex binds to promoter region to regulate gene expression in DNA

why do some animals have sexual reproduction

-produced more genetic variation in offspring

(asexual reproduction: pathogenesis, all eggs identical to parent)

appetitive male sexual behavior

-sex drive, interest, motivation

ex. vocalizations, movement in search of mates

-can measure via operant conditioning in rodents

consummatory male sexual behavior

copulatory behavior (discrete, actual sexual behavior)

-can measure mounting, intromission, ejaculations in rodents

-reliable and consistent measures

organizational effects of androgens

-relatively early: prenatal, neonatal, adolescence (critical period)

-longer lasting

-structural , biochemical changes

activational effects of androgens

-in adulthood/after adolescence

-shorter effects (transient)

-no critical period

-structural, biochemical changes

androgens do not directly cause male sexual behavior, but rather change the (__________________________________) in a particular context

-not a trigger

androgens do not directly cause male sexual behavior, but rather change the probability that male sexual behavior will occur in a particular context

what was the hypothesis for Young’s experiment (reproductive behavior in rodents)

hormones in early development are important for reproductive behavior in adulthood

methodology for Young’s experiment (reproductive behavior in rodents)

T or oil (vehicle) injected to pregnant guinea pigs

→ female offspring: neonate female offspring all had ovariectomy (OVX), adults had E2+PROG or T or oil injected

result of female prenatal OIL → adult E2+PROG (Young’s experiment)

lordosis

result of female prenatal T → adult E2+PROG (Young’s experiment)

reduced lordosis (giving testosterone does not change behavior)

result of female prenatal OIL → adult T (Young’s experiment)

no mounting (adult females do not respond to T manipulations)

result of female prenatal T → adult T (Young’s experiment)

mounting

result of male prenatal SHAM → adult T (Young’s experiment)

mounting

result of male prenatal GDX → adult T (Young’s experiment)

reduced mounting (adult males respond to T manipulations)

result of male prenatal SHAM → adult E2+PROG (Young’s experiment)

no lordosis

result of male prenatal GDX → adult E2+PROG (Young’s experiment)

lordosis

critical period

increased sensitivity to effects of hormones on behavior

activational effects of estrogens

-expressed in specific brain regions (immunohistochemistry, in situ hybridization-design a probe with labeling)

-GDX+T adult male rats had a restoration of testosterone (systemic aromatase inhibitor or saline treatment)

-systemic T or E2 or oil treatment for GDX adult male rats

what happened during the experiment with Japanese quail on estrogens and male appetitive sexual behavior

-male will look at female through window (sexual interest)

-GDX reduces time at window

-T treatment of GDX males restores time at window

acute effects of estrogens on male appetitive sexual behavior

-method: one s.c. injection of saline control (C) or vorozole (VOR, aromatase inhibitor), or VOR+E2

-time at window measured after 10 min

→ aromatase inhibitor had significant effects in reducing time at window

how to determine where androgens and estrogens act to regulate male sexual behavior?

immunohistochemistry, autoradiography, etc.

where are sex steroid receptors located in the brain

clusters in amygdala, lateral septum, preoptic area, , hypothalamus, pituitary, hippocampus, tectum

(ALPHPHT)

what does this diagram show

no activity in anterior hypothalamus during sexual activity

what does testosterone facilitate

release of dopamine in the mPOA (medial preoptic area) and other areas

after androgen is converted to estrogen, which two sites does it act on

medial preoptic area (mPOA) and medial amygdala

estrous cycle in female rodent sexual behavior

-4 days

-ovulation happens at the end of proestrus stage (behavioral estrus)

-nocturnal, breed at night

-can only get pregnant during estrus

what happens during behavioral estrus of female rodent estrous cycle

-appetitive sexual behavior (proceptivity-motivation, female initiation of copulation)

-consummatory sexual behavior (receptivity-responsiveness to male initiation of copulation)

measurements of female consummatory behavior

LQ: Lordosis Quotient

(lordosis: stereotypical posture and expression, robust and easy to measure)

-OVX in rats greatly reduces lordosis

female brain region not activated during sexual behavior

lateral septum is not active

estrogen receptors in brain

-autoradiography with labeled E2 used

-ERs in vlVMH (ventrolateral ventromedial hypothalamic nucleus) critical especially for male sexual behavior

-X ray shows anything that binds to estradiol

regulation of lordosis in female rodents

-E2+PROG sequentially is more effective at inducing lordosis than E2 alone

-lordosis is restored by E2+PROG in OVX adult rats (PROG after 2 days)

-estradiol primes the brain to be more sensitive to PROG and they work together to stimulate behavior

what would the VMH look like for control (oil) vs E2 treatment in OVX rats

many more PROG receptors bound to antibodies with E2 treatment than control

lordosis circuit (female rodent)

VMH → periaqueductal gray → medullary reticular formation → reticulospinal tract → spinal cord

role of forebrain in reproductive behavior/lordosis

inhibits lordosis

role of hypothalamus in reproductive behavior

responds to steroid hormones, produces proteins and peptides

role of midbrain in reproductive behavior

receives hypothalamic peptides, changes slow to fast signaling (contains mesencephalic flexure)r

role of lower brain stem in reproductive behavior

integrates posture across segments

role of spinal cord in reproductive behavior

each segment receives stimulation, receives descending information, produces motor response

autoradiography

used to determine the tissue (or cell) localization of a radioactive substance, either introduced into a metabolic pathway, bound to a receptor or enzyme, or hybridized to a nucleic acid.