Lecture 8: Reproductive Behavior and Endocrine Disrupting Chemicals Flashcards
Definition Sexual behaviours
Set of actions with the primary aim of ensuring that the male sperm is delivered successfully to the female ova.
- main evolutionary behaviour to deliver sperm to ova.
Definition sex drive/libido
motivational force that drives individuals to seek out members of the opposite sex and copulate with them.
Definition Physiological costs
Female eggs are ‘expensive’ to produce, and are limited in supply, while male sperm is ‘cheap’.
- These behavioral specializations into nurturing effort versus mating effort led to clear differences between the sexes.
- in general, there is a higher cost for females, evolutionarily and physiologically, in terms of raising the offspring.
Two- stage distinction of sexual behaviours
- For most animals, sexual behaviors occur in a sequence of fairly well-defined stages. At each stage the individual must be responding to both internal (hormones) and external (context, social position, partner receptivity) factors, each of which is having some influence on the current behavior.
- Initially sexual behaviors were defined in terms of ‘appetitive’ and ‘consummatory’ stages. This two-stage distinction has since been applied to other behaviors such as feeding, aggression and drug-taking behaviors in both animals and humans.
Appetitive behaviors: responses that bring the individual into contact with the particular goal at hand (e.g, sexually receptive individual) - ie: addiction research, always understand the environment of the patient, because certain circumstances might drive specific behaviours (same thing with sex).
Consummatory behaviours are performed when individuals are in contact with their primary goal, and they tend to be more highly stereotyped and species-specific, and are probably innate
Components of male sexual behavior behaviors:
Mount latency - time from when a male and female are first introduced to when the first mount occurs. Male rat takes time to mate with a female (this is mount latency).
Intermission latency - time from when they are first engage in penile penetration
Ejaculation latency - time between the first intromission and ejaculation.
Postejaculatory refractory period– time between ejaculation and resuming sexual search.
- We can correlate these with hormonal levels
- The shorter these latencies, the stronger the male/female sex drive.
- When defining important behaviours in females we use males…weird.
Components of female sexual behavior behaviors:
Attractivity - stimulus value of the female to a male; for example, if a male chooses to spend more time with a particular female. more attractive female = male spends more time with her.
Proceptivity - extent to which a female will initiate sociosexual encounters with males, and thus reflects both her overt behaviors and her underlying motivational state. More specific to females.
Receptivity - state of responsiveness of the female to the sexual initiation of the male (i.e., lordosis - to expose genital organ).
- Use these behaviours to try and measure sex drive and sexual rate
- The shorter these latencies, the stronger the male/female sex drive
Hormones and sexual behaviors in males (animal models): Pheromones
Pheromones - smearing immobilised male hamsters with vaginal secretions from an estrous female, leads to other males attempting to mount these hapless males. Immobilized males free from pheromones did not elicit this behavior in other males. The presence of a female can elicit these sexual behaviours - certain pheromones will trigger the response in males.
- female pheromones are a potent signal in mice. If males are exposed to female pheromones, it will elicit sexual response.
Regions that are essential to the control of sexual performance in male rats
- The preoptic area (POA) appears to be especially important for the integration of environmental, physiological, and psychological information prior to and during successful copulation; POA lesions reduce or eliminate male sexual behavior in virtually every vertebrate species.
- Preoptic neurons project to several places in the brain, including the dopaminergic neurons in the ventral tegmental areas (VTA) - main source of dopamine.
- POA lesion destroys the connections to these dopaminergic neurons and impairs the POA regulation of dopaminergic activity.
- Drugs that increase dopamine synthesis or stimulate postsynaptic dopamine receptor sites should also facilitate copulatory behavior in males. (ie, MDMA - leads to euphoria, emotional warmth and increased energy and libido elisted by this drig).
- Beyond testosterone, approximately a 50% increase extracellular dopamine in the mPOA is associated with higher copulation, regardless of testosterone concentrations.
- Females will be more receptive in the ovulation phase of their menstrual cycle. They have higher levels of estrogen and higher levels of progesterone after ovulation is associated with a higher aggressiveness and territorial aggressiveness in other animals as well.
- In general, testosterone would have a higher role in males for sure and estrogen would have a higher role in females. Progesterone in females would be the other part of the cycle in which they are less receptive and a lottle more aggressive towards males.
- If we inject testosterone in males, we see an increase in sexual behaviors. Same if we inject estrogen.
Hormones and sexual behaviors in Men
How to measure? Sexual desire
Sexual desire: subjective psychological state in which the individual displays an interest in sexual stimuli, and is motivated towards seeking out sexual activities, though may not necessarily be sexually aroused.
Hormones and sexual behaviors in Men
How to measure? Sexual arousal (defined in two forms)
Sexual arousal: - a two-part process: the first reflects
physiological – genital sexual arousal, and the second is the subjective awareness that one is genitally and/or physiologically aroused
- Objective measures such as heart rate and blood pressure monitoring, latency to achieve orgasm, measurement of penile erection via a penile plethysmograph.
- Penile plethysmograph measures the volume of displaced air as the penis became enlarged. It was designed to prevent young males from avoiding military service by pretending to be homosexual. The device was placed over their penis, and they were shown erotic heterosexual material. The air displacement would provide their “manliness” to fight. Also used to see if people were pedophiles
Effects of testosterone treatment on
hypogonadal men
- We assume that higher levels of testosterone are associated with higher levels of sexual behaviours. This is generally true.
- Hypogonadism refers to a condition in which the body produces insufficient levels of sex hormones (lower concentrations).
- Men with low concentrations of blood plasma testosterone (<3 ng/ml) received three injections 6 weeks apart. Add more testosterone and we see them increase in total erections, nocturanal erections, coital attempts, masturbation, orgasms)
Study groups:
1- placebo (oil vehicle alone)
2 - low (100 mg)
3- high (400 mg) doses of testosterone
Patients’ self-reports indicated that the incidence of erections and certain sexual behaviors also increased in a dose-dependent manner.
Effects of testosterone treatment on
“normal” men
- In the study, weak evidence of testosterone and sexual behavior was observed in men with regular levels of testosterone.
- The testosterone intervention group showed an increase only for the search of auditory or visual sexual stimuli. Other behavioral measures (e.g. masturbation, sexual intercourse, etc.) showed no differences between the groups.
- Currently it is understood that once a threshold of serum testosterone has been achieved (around the low normal range) this is sufficient to normalize sexual function and motivation. Thus, Increasing testosterone levels to the high normal range had no additional effect on sexual behaviors.
- Same with estrogen, it can also raise the sexual behaviour but only to a certain extent.
- Regular males, adding testosterone is not leading to more sexual behaviours.
The human menstrual
cycle
First day is marked by the menstruation.
1) Menstrual Phase (Days 1-5): Occurs when the uterine lining, which has thickened in preparation for pregnancy, is shed in the absence of fertilization. It’s characterized by menstrual bleeding, which typically lasts for about 3 to 7 days. The shedding of the endometrium is triggered by a decrease in estrogen and progesterone levels.
2) Proliferative Phase (Days 6-14): Following menstruation, the proliferative phase begins as the ovaries in response to FSH start to produce increasing amounts of estrogen. Estrogen stimulates the growth and thickening of the endometrium, preparing it to receive a fertilized egg (embryo) in the event of conception.
3) Ovulation (Around Day 14): Ovulation marks the midpoint of the menstrual cycle and typically occurs around day 14. It is triggered by a surge in luteinizing hormone (LH) from the pituitary gland, which causes the dominant ovarian follicle to release a mature egg (ovum) into the fallopian tube. Ovulation is a key event for fertility, as it is the most fertile period of the menstrual cycle.
- progesterone is important for the building of the egg.
4) Secretory Phase (Days 15-28): After ovulation, the secretory phase begins, characterized by the secretion of progesterone from the corpus luteum, which forms from the collapsed ovarian follicle after ovulation. Progesterone helps to further thicken the endometrium, making it more conducive to embryo implantation. If fertilization and implantation do not occur, the corpus luteum regresses, leading to a decline in progesterone levels.
Which hormones would be more important for sexual behaviours during the cycle?
- estrogen during ovulation = higher probability of reproduction.
- Women will engage more in sexual behaviours during ovulation period.
Facial preference test
Women in the follicular phase are attracted to more masculine faces such as the one on the left.
Examples here are versions of a composite male face that has been computer-manipulated
(A) increase and (B) decrease the masculinity of a man’s face.
Main correlational (it is not causal) findings: Follicular phase
- Greater preference for more masculinized and more symmetrical male faces.
- In a short-term relationship, preference for a masculinized.
- In an experimental sexually eliciting setting it is observer a higher level of sexual arousal (both subjective and objective).
- Higher probability of short-term encounters, and flirting with men other than their current partner.
Main correlational findings: Lutheal phase
Lutheal Phase
- Preferences for the apparent health displayed in male faces (more healthy).
- Such preferences for an apparent health were stronger in pregnant women (high progesterone), and in women using an oral contraceptive.
- Estimated progesterone levels were positively related to preferences for femininity in male faces, and women in a stage of high estimated progesterone showed more commitment to their relationships
Women equivalent to animal attractivity phase?
In this study, women (not taking Birth Control) were asked to wear a T–shirt for three consecutive nights during their late follicular (ovulatory) phase and another T–shirt during the luteal (non-ovulatory) phase of their menstrual cycle.
Male raters judged the odors of T–shirts in terms of
sexiness and pleasantness –> more attractive in the follicular phase. Ovulating was the most attractive and sexy
These findings were replicated with ratings of pictures.
Pictures of women with higher estrogen levels were viewed as being more feminine, attractive and healthy than those representing females with lower estrogen levels
The human menstrual cycle and
contraceptive pills
As pill-users have a relatively stable levels of progesterone and Estrogen throughout their cycle, it is observed lower sexual behavior variations during the cycle. In this case, testosterone seems to be more relevant in this scenario.
In pill contraceptive users, free testosterone was significantly positively related to sexual thoughts, sexual desires and the anticipation of sexual activity.
- no ovulation in people taking the pill.
- not all the pills are the same during the cycle –> this is because we still want to see the cycle (placebo pill).
- We have an active and inative pill phase (huge drop in progesterone levels), then we have menstruation. People always take the active pill to skip their menstruation (progesterone is always high).
- We usually observe a lower level of sexual behaviour. Progesterone levels are associated with more stable relationships in women.
- Estrogen levels when on the pill is very low, and estrogen levels is associated with more sexual behavior and higher infidelity.
Risks of taking the pill for long:
- embolism
- altering the cycle
- Higher probability of incidence of cancer
Taking the pill helps with PMS.
Does the contraceptive pill alter mate choices in humans? changes in females
Normally cycling women (non-pill users) preferred fewer masculine faces in a long-term context compared with a short-term context. For pill users this difference disappeared.
Does the contraceptive pill alter mate choices in humans? changes in males
In similar fashion, men show preference for women in the fertile phase of the menstrual cycle with a short-term context. By contrast, pill users showed no change in interest the fertile phase, suggesting that the use of pill interrupts cycling attractiveness of women to men.
High levels of progesterone can alter how men view women and how women view men.
EDCs
Key characteristics
Mechanisms by which EDCs can disrupt the endocrine system. It can interfere in almost all aspects of the endocrine system.
Where can you find EDCs
- mainly from pesticides: contaminate food, wheat and soil
- Children products: BPAs
- Shampoo (glowly shampoo with sparkles) - Use organic products, products with less weird names in the composition.
Bisphenol A (BPA)
found in plasticizers (key disrupters). It is used to make plastic harder.
* Known deleterious mechanins of action on estrogen and androgen receptors.
* Hormones important for female and male sexual and reproductive development
* BPA has been linked to hormonerelated side effects including infertility and breast and prostate cancers.
Sewage system to treatment facility
Routes of exposure to EDCs
- Simple contact from mother to fetus
- several ways
5Α-REDUCTASE
DEFICIENCY
- Genetic males (XY) with 5α-reductase deficiency are born with ambiguous genitalia and small, undescended testes. Leads to inhibition of DHT conversion of testosterone. DHT is needed for sexual differentiation.
- They are usually considered females at birth and reared as females. At puberty, testosterone masculinizes the body, which develops male-typical musculature and axillary hair growth, and the genitalia develop to resemble a male-typical penis and scrotum.
- Exposure to EDCs is associated with higher rate of this deficiency.
