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Behavioral Endocrinology > male reproductive behavior > Flashcards

male reproductive behavior Flashcards

1
Q

sperm cells

A

modified gametes carrying haploid components of DNA; one cell of the testis

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2
Q

sertoli cells

A

nourish sperm during maturation, source of androgen-binding protein (sperm need ABP to travel in the blood because androgens are steroids and hydrophobic); source of inhibin (role in negative feedback on AP) and MIH; associated with FSH; located within seminiferous tubules

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3
Q

Leydig cells

A

source of androgen (testosterone); mediated by LH; located in interstitial tissue in seminiferous tubules

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4
Q

sperm

A

cycle of production occurs every 2 months; 200-500 million sperm per ejaculate; originate and mature in the seminiferous tubules and epididymis

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5
Q

seminal fluid

A
  • produced by the seminal vesicle and prostate
  • serves as an aqueous buffer for sperm transport
  • composed of sugars, amino acids, vitamins, prostaglandins–> nourish the sperm
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6
Q

seminal plug

A

coagulation of semen at the vaginal entrance; prevents leakage

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7
Q

spermatogenesis

A

LH–> testosterone–> spermatogenesis

  • Process:
  • spermatogonia (precursor to sperm) undergo mitosis to produce a)other spermatogonia b)primary spermatocytes
  • primary spermatocytes under meiosis 1 to produce 2 secondary spermatocytes
  • secondary spermatocytes undergo meiosis 2 to produce 4 spermatid
  • spermatid mature into sperm
  • sperm travel through lumen of the seminiferous tubules to the epididymis–> vas deferens
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8
Q

seminiferous tubules

A

where the sperm originate and mature

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9
Q

steroidogenesis

A

the creation of steroids

  • testosterone synthesized in the leydig cells under the influence of LH
  • (this T acts on the sertoli cells to stimulate spermatogenesis)
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10
Q

aromatization of T->E

A

testosterone is aromatized to estradiol in the sertoli cells under the influence of FSH

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11
Q

pathway of Testosterone conversion in Leydig (cholesterol)

A

-LH–> activation of G-coupled protein receptor–> activation of adenylate cyclase and synthesis of cAMP–> PKA activation–> enzyme amplification–> conversion of cholesterol–> pregnenolone–> progesterone–> androstenedione–> testosterone

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12
Q

FSH, sertoli cells, ABP

A

FSH stimulates the sertoli cells to produce ABP

-FSH acts as a transcription factor (and ultimately translation factor) that leads to the synthesis of ABP

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13
Q

testosterone metabolites

A

testosteroneandrostenedione
testosterone–> DHT via 5-a reductase
testosterone–> estradiol via aromatase

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14
Q

negative feedback of testosterone

A

testosterone produced from leydig cells feeds back on the AP and hypothalamus to decrease GnRH, LH, and FSH

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15
Q

negative feedback of inhibin

A

inhibin produced from sertoli cells feeds back on AP to decrease FSH secretion

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16
Q

male sexual behavior

A

all behaviors necessary to deliver the sperm to the ova

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17
Q

appetitive phase

A

all behaviors a male uses to gain access to a female

  • aka: courtship, sex drive, appetitive behavior
  • seeking sexual encounters, flirting
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18
Q

consummatory phase

A

time when copulation occurs; sex behaviors

-associated with performance, copulation, potency

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19
Q

sex drive (part of appetitive phase)

A

associated with motivation; the motivational force that brings individuals to sexual union

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20
Q

obstruction test

A

one way to measure male motivation/sex drive in rats

-must cross an electrical grid to gain access to a female; time=measurement of motivation

21
Q

bar pressing

A

one way to measure male motivation to engage in sex

22
Q

mount

A

pelvic contact without penile insertion

23
Q

intromission

A

penile insertion, strong dismount, genital grooming

24
Q

ejaculation

A

deep thrust, forceful explosion of semen, weak dismount, post-ejaculatory interval

25
Q

copulatory lock

A

animals remain attached b/c penis swells in size and cannot physically leave females body

  • maintains sperm transport
  • bad in nature because it may leave you vulnerable to predators
  • only seen in non-prey species, nocturnal species
26
Q

testosterone maintenance and restoration

A
  1. castration and immediate testosterone replacement will MAINTAIN sex behavior in a dose-dependent manner (increasing levels of T bring an ind. closer to pre-castration levels)
  2. castration+ long wait period (no more free-floating testosterone circulating in the blood)+ T replacement–> RESTORE sex behavior

-independently will restore mounts, intromissions, and ejaculations

27
Q

effects of castration on sexual behavior

A

decreased sexual responsiveness, motivation, and performance (decreased sex behavior and sex drive)

  • will not investigate females, will not work nor suffer pain to contact them
  • species differentiate in how long after castration that sexual behaviors cease
28
Q

why are higher doses of testosterone needed to restore rather than maintain sex behavior

A

persistent exposure of the brain and sensory neural tissue to androgens preserves their responsiveness to those hormones (the number of androgen receptors will decrease if not surrounded by circulating androgens)

29
Q

order of disappearance of sexual behaviors post-castration

A
  1. ejaculations
  2. intromissions
  3. mounts
30
Q

how to test effects of hormonal metabolites

A
  1. castration, hormonal replacement with metabolite of interest
  2. inhibition of enzymes (aromatase, 5a reductase)
  3. injection of agonist, antagonist
  4. receptor blockers
31
Q

role of estradiol in male sexual behavior

A

testosterone effects the maintenance and restoration of male sex behavior only through its conversion to estradiol, and estradiol’s subsequent action

  • ACTS ON THE CNS
  • DHT does not restore reproductive behavior/maintain it, cannot be converted to estradiol (however, T and androstenedione can)
  • will independently restore mounts and intromissions, but NOT ejaculations
32
Q

role of DHT in male sexual behavior

A

acts of the periphery to regulate penile sensitivity and responses

  • changing penile shapes associated with different hormone levels and stage of reproductive behavior
  • **will not restore any mating behaviors UNLESS in conjunction with estradiol
33
Q

mPOA role in male performance

A

MPOA lesions eliminates male PERFORMANCE, but not motivation
-MPOA stimulation–> faster ejaculation

34
Q

mPOA and dopamine

A

testosterone and estradiol act on the MPOA to release dopamine–> genital reflexes and sex motivation

35
Q

Elaine Hull: Microdialysis and MPOA

A
  • found that dopamine levels in the MPOA increase in males in the presence of sexually receptive females
  • dopamine levels did NOT increase if the female wasn’t in estrus
  • drugs that stimulate dopamine synthesis and release–> facilitation of copulation
  • drugs that block dopamine–> decrease in M sexual behavior
36
Q

role of dopamine in male sexual behavior

A

dopamine removes the tonic inhibition of the MPOA and leads to greater sensorimotor integration

37
Q

role of the MPOA

A

integration of internal and external information: auditor, olfactory, tactile cues that are associated with the time of day, **stimuli associated with an estrous female, endocrine state of the male, **memories associated with previous sexual encounters

38
Q

role of the olfactory bulbs in male sexual behavior

A

interact for successful mate recognition and sex behavior

  • detection of CHEMICAL SMELLS
  • blocking of smell–> decreased social and reproductive behaviors
39
Q

role of the VNO in male sexual behavior

A
  • detection of PHEROMONES
  • VNOX eliminates some sexual behaviors in some animals
  • detection of non-volatile components of chemosensory stimuli (i.e. urine) to prolong contact with appropriate mating partners (i.e. estrous female)
  • nerves from the VNO terminate on the olfactory bulbs
40
Q

role of the amygdala in male sexual behavior

A

lesions of the amygdala lead to DECREASED MOTIVATION but do not hinder performance

  • receives projections from the VNO and olfactory bulbs
  • projects to the MPOA via the stria terminals (lesioning of the ST can also decrease M motivation to engage in copulatory behaviors)
41
Q

neural circuit mediating male sexual behavior

A
  1. information is integrated in the MPOA
  2. projection to the periaquaductal gray
  3. projection to the nucleus gigantocellularis
  4. information transmitted to the spinal cord neurons that project to the pudendal musculature and cells that regulate penile reflexes
42
Q

testosterone, MPOA, dendritic spine density

A

Jennifer Swann

  • castration leads to decreased dendritic spine density in the MPOA, but not the LPOA
  • testosterone injections in the MPOA increase DS number, but not length
  • why is this relevant? more dendritic spines–> more connectivity–> more neural activity–> increased likelihood of behavioral activation
43
Q

testosterone replacement and MPOA responsiveness to urine

A
  • urine of estrous females increases the neural activity in both the olfactory bulbs, VNO, and MPOA
  • castration: still neural activity in the olfactory bulbs (implies that chemosensory cues from females are still processed at an early level of sensory input to the brain) but NOT in the MPOA
  • testosterone replacement restores MPOA responsiveness to estrous urine
44
Q

Biological basis of gay rams

A

oSDN of male-oriented rams 2-3x smaller than in female-oriented rams, of similar size to female rams
-neuron count in oSDN (ewes (fewest)–> male-oriented–> female oriented))

45
Q

organizational effects of testosterone on the oSDN

A

sex differences in SDN-POA and mating behavior arise out of exposure and organizational effects of testosterone and estradiol during the perinatal period
-difference in size of the oSDN is NOT impacted by concentrations of hormones in the blood (T and E have organizational, but not activational effects)

46
Q

timeline of genital vs. brain masculinization

A
  • genitals masculinized days 30-60
  • oSDN masculinized days 60-90
  • testosterone affects the differentiation of the genitals and brain in different timeframes, so while a ram’s sex is male, varying levels of T exposure may masculize the brain differently and explain why we see differences in sexual partner preference
47
Q

HPG axis and masculinization of the body and brain: gay rams

A

HPG axis is established very early in development to maintain homeostasis and ensure there’s enough testosterone produced to complete testicular development and regulate brain masculinization
-kisspeptin stimulates GnRH neurons in the hypothalamus–> stimulate the AP to produce LH–> production of testosterone in the testis–> brain masculinization and testicular development

48
Q

garter snakes and dissociated reproductive pattern

A

reproductive behavior does not coincide with maximum gonad size and activity

  • copulation occurs when steroid levels and gamete production are low
  • produce when there is no free floating testosterone, testes are regressed)
49
Q

garter snakes: influence by MPOA and pineal (NOT castration, steroids, or gonadotropins)

A

sexual performance and motivation can be eliminated by lesioning the MPOA or pineal gland: two regions that integrate environmental information that allows the snake to process seasonal information

Behavioral Endocrinology (12 decks)

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