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Hormones & Behavior > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

AVPV

A

AVPV regulates ovulation and it is the source of a sexually dimorphic projection to the arcuate nucleus

Which sex is the AVPV larger in? females

AVPV are important in the secretion of? GnRH

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2
Q

Male reproductive behavior

A

Sexual motivation is strong in males

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3
Q

Ultimate cause of sexual behaviors in males vs. females

A

Gametes…..
Eggs are relatively large and limited in supply
Sperm are relatively small and not limited (almost disposable)

Parental investment…..
Female Mammals: Pregnancy & Lactation
Invest more in their offspring than males

Reproductive fitness…..
Females: “choosy”
They must choose the best possible males with whom to combine their genes.
Males: “ardent” Mate with as many females as possible

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4
Q

Sexual behaviors

A

behaviors that evolved to bring the two gamete types together

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5
Q

Sexual attraction

A

what is necessary to bring the two sexes together, i.e. appearance, smells

In many species, sexual attraction is closely synchronized with peak fertility and the physiological readiness to reproduce

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6
Q

Male sexual behavior

Divided into 2 phases:

A

Appetitive – courtship (singing, fighting the competition, strutting, etc.)

Consummatory – copulatory behavior

Males spend much more time and energy seeking copulation than actually copulating!!

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7
Q

Male sexual behavior in rodents

A

Sexual attraction is largely olfactory

Appetitive behavior:

Consummatory behavior:
Mounting
Intromission
Ejaculation

Post-ejaculation:
Ultrasonic vocalizations 
Self-grooming
Post-ejaculatory interval
Satiation if PEI is greater than 90 minutes
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8
Q

Coolidge Effect

A

The propensity of an animal that has appeared sexually satiated with a present partner to resume sexual activity when provided with a novel partner

The President and Mrs. Coolidge were being shown [separately] around an experimental government farm. When Mrs. Coolidge came to the chicken yard, she noticed that a rooster was mating very frequently. She asked the attendant how often that happened and was told, “Dozens of times each day.” Mrs. Coolidge said, “Tell that to the President when he comes by.” Upon being told, the President asked, “Same hen every time?” The reply was, “Oh, no, Mr. President, a different hen every time.” President: “Tell that to Mrs. Coolidge.”

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9
Q

Typical measurements

A

Measures of sexual motivation:
Mount latency
Obstruction tests

Measures of sexual performance:
Inter-mount interval, inter-intromission interval
Number of mounts and intromissions prior to ejaculations
Ejaculation latency

Measures of mating potential:
Number ejaculations
Number of ejaculations prior to sexual satiety

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10
Q

Endocrine mechanisms in rodents

A

Androgens play an important role in males sexual behavior

After puberty…
Sexual motivation is expressed
Sexual performance and copulatory ability increase

Castration reduces sexual behaviors and sexual motivation

Order of loss:
days, longer latency to initiate mounting and intromissions, fewer intromissions prior to ejaculation
1-2 weeks no ejaculation
After 2-3 weeks, decline in the number of mounts and intromissions
Finally Male no longer mounts

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11
Q

Effects of experience

A

Sexual experience can have a large impact on the effects of castration in many animals.

Sexually inexperienced rats will show rapid decrease in sexual behavior after castration.

Many males with prior sexual experience will continue to mate for weeks after castration.

What changes?

The effects of castration on male rodent reproductive behavior can be reversed by testosterone treatment

Order of restoration:
Mounts, intromission, ejaculation

Sequential reappearance of behavior suggests differing hormonal sensitivities

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12
Q

Maintenance vs Restoration in rats

A

Maintenance: given T immediately after castration

Restoration : T treatment began after all sexual behaviors stopped

Receptor number
Muscular atrophy

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13
Q

Aromatization - rodents

A

T exerts its activational effects on mating behavior via aromatization to estradiol:

In castrated rats, T and estradiol induce appetitive and consummatory male sexual behavior

T plus aromatase inhibitor reduces males sexual behavior

Aromatase knockout mice and alpha-beta ER knockout mice have deficits in sexual behavior

5α-DHT (product of T that can’t be converted to E) does not prevent post-castration decline in reproductive behavior

DHT is important in the periphery to maintain penile reflexes and tactile sensitivity

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14
Q

Individual Differences in Male Mating Behavior

A

Hypothesis: animals with high sex drive had higher T levels that animals with low sex drive

Individual differences in sexual behavior are NOT determined by individual differences in androgen levels

Males identified as copulators or non-copulators

All had T concentrations of 2-3 ng/ml

Copulators were castrated and implanted with testosterone capsules

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15
Q

What accounts for these individual differences between copulators and non-copulators?

A

amyloid beta precursor protien

Sometimes its an unexpected biological player: APP

Amyloid B precursor protein (APP) levels are higher in persistent copulators…

APP transgenic mice are also resistant

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16
Q

Behavior Affects Hormones

A

A rise in testosterone is seen in males during mating and prior to mating in response to sensory cues associated with females

This response can be classically conditioned

17
Q

Remember

A

It is NOT accurate to say that androgens cause sexual behavior!

Instead, androgens affect the likelihood of mating behaviors in the presence of the appropriate stimuli in the appropriate social context.

18
Q

Brain mechanisms of rodent male sexual behavior

A

Olfactory system
Amygdala
MPOA

19
Q

Olfactory system

A

Olfactory bulbectomy and destruction of the vomeronasal organ (VMO) reduces male attempts to mate

VMO detects pheromone signals

20
Q

Amygdala

A

Major input:

Lesions of basolateral: amygdala reduces appetive

Lesions of Corticomedial: amygdala disrupts consummatory

Hormone receptors

Fos (IEG) and mating

21
Q

Where does the amygdala project to induce sexual behavior?

A

MPOA

22
Q

MPOA

A

Critical for integrating various internal and external stimuli prior to and during copulation including environmental, sensory, physiological, and psychological info

23
Q

Evidence that MPOA regulates male
 sexual behavior

A

Lesions of the MPOA

Electrical stimulation of the MPOA

Autradiographic studies have shown that the MPOA contains androgen and estrogen receptors

Using in situ hybridization, aromatase mRNA has been detected in the MPOA

Implants of T into the MPOA of castrated males facilitates sexual behavior, but not if given with an aromatase inhibitor

Fos expression

24
Q

Castration reduces neural responsiveness
 in the MPOA

A

Odour of estrous females produces electrical activity in the olfactory bulbs and the MPOA
Remove and replace:

25
Q

Output pathways that regulate

male sexual behavior

A
  • Nucleus paragigantocellularis (PGN) has serotonin fibers that normally inhibit the erection response
  • mPOA signals counteract the inhibition
  • Sexual side effects of SSRIs and output pathways:
26
Q

Dopamine and male sexual behavior

A

POA lesions destroy connections to dopamine neurons in PAG and VTA

Pharmacology (agonists and antagonists):

extracellular DA in MPOA increases in response to cues from an estrous female

27
Q

What brain region seems to be important in male orgasm?

A

VTA

28
Q

Chemical castration significantly reduced androgen levels but is ________ in reducing sex drive

A

ineffective

29
Q

Gonads are _____ to increase the probability of a sexual response in the presence of appropriate stimuli

A

unnecessary (i.e. hypogonadal males- in hypogonadal men they don’t have their testes making the appropriate amount of androgens but they can still respond with feelings of sexual desire when looking at a photo of a naked female)

30
Q

In normal men, neither blocking estrogen receptors nor treating them with an aromatase inhibitor has any effect on sexual behaviors

A

unlike rodents

another difference between humans and rodents

31
Q

________ have a strong activational effect in men

A

androgens

32
Q

Things to know about Brown-Sequard:

A

injected himself with grinded up organs of dog and pig testes and decided he felt great after

33
Q

What is the role of dopamine in male sexual behavior?

A

Dopamine appears to facilitate male sexual behavior by removing tonic inhibition of brain regions that mediate sensorimotor abilities

34
Q

How does POA lesions impact dopamine release?

A
  • Major effect of POA lesions: destroying connections to dopaminergic neurons in PAG and VTA
  • Dopamine (DA) agonists can provide some restoration
  • In intact rats, DA agonists facilitate mating behavior whereas antagonists suppress mating
  • Microdialysis studies show that extracellular DA in MPOA increases in response to cues from an estrous female
35
Q

When the MPOA is activated, what effect does it have on the PGN

A

its signals counteract the inhibition from the PGN motor output- mounting & thrusting

36
Q

What are the sexual side effects associated with SSRIs?

A

difficulty achieving erection, ejaculation and or orgasm, due to enhanced effectiveness of PGN released serotonin in the spinal cord

Hormones & Behavior (6 decks)

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