AFFILIATIVE + REPRODUCTIVE BEHAVIOUR

Question 1

Castration and Hormone replacement

Answer 1

Testis transplantation restores normal development in rooters. Transplanted testes were not connected to blood supply or neuronal networks. Their effect was mediate by chemicals released to their blood stream. Testis transplant from farm animals was also tested in humans with ‘weak sexuality’ -> Brinkley’s surgeries were a success for some time, but ethical, methodological, and safety aspects made this enterprise unsustainable. Note: Viagra, introduced in 1998, produced $1B sales that year, highlighting the market for sexual enhancers.

Question 2

What are hormones?

Answer 2

Hormone -> signalling molecular that can carry messages to distant targets through the blood stream (e.g., testosterone). Neurohormone -> a hormone released by neurons. Targets neighbouring or distant cells (e.g., oxytocin). Target: organs/cells that can detect hormone/s and it is affected by it/them.

Question 3

Hormone Classes

Answer 3

Steroid hormone, anime hormone, peptide and protein hormones.

Question 4

What are steroid hormones?

Answer 4

derived from cholesterol, they can travel across cell membranes. e.g., cortisol and progesterone.

Question 5

What are amine hormones?

Answer 5

derived from the amino acid tyrosine -> cannot cross the cell membrane e.g., thyroid hormone.

Question 6

Peptide and protein hormones

Answer 6

amino acid chains -> cannot travel through the cell membrane -> activate membrane receptors e.g., oxytocin, vasopressin (peptides), prolactin (protein).

Question 7

Where are hormones produced?

Answer 7

Sex hormones -> testes for male, ovaries for female (oestrogen, progesterone).
Non-Sex hormones -> growth hormone (GH) from pituitary gland -> thyroxine (TH) from thyroid gland -> insulin from pancreas -> adrenaline (ADH) from adrenal gland.

Question 8

Development of Genetic Sex

Answer 8

Offspring genetic sex depends on the sex chromosome carried by the sperm and egg (ovum) that generates them. Genetic sex depends on the father sperm cells, which carry X or Y sex chromosomes -> All the information to develop bodies of either sex is present in the 22 non-sex plus the X chromosomes (not Y chromosome) -> Exposure to sex hormones, both before and after birth, is responsible for sexual dimorphism -> The Y chromosome controls the development of the glands that produce the male sex hormones -> Sex organs: gonads (ovaries and testes), internal sex organs, and external genitalia.

Question 9

What are gonads?

Answer 9

Gonads (testes or ovaries) are the first to develop -> produce ova or sperm and hormones -> sex-determining region Y (SRY) gene (from Y chromosome) expresses SRY protein that differentiates gonads into testes -> lack of SRY results in ovaries development.

Question 10

Internal Sex organs?

Answer 10

During the first two months of gestation, foetus can develop into either male or female -> At month three, if testes are present and producing hormones (anti-Müllerian hormone and androgens) -> the internal sex organs develop into male ones -> Female internal organs do not need the presence of any other hormone to develop.

Question 11

What is External Genitalia?

Answer 11

As with internal sex organs, external genitalia do not need hormonal influence to develop into female organs -> Dihydrotestosterone (androgen produce by testes) develops external genitalia into male version.

Question 12

What is sexual maturation?

Answer 12

Secondary sex characteristics develop during puberty and are also influenced by hormones. E.g., enlarged breasts and widened hips on females, facial hair and Adam’s apples on males, and pubic hair on both -> The hypothalamus release gonadotropin-releasing hormone (GnRH), which ultimately stimulates hormone release by testes or ovaries -> testes release testosterone -> ovaries release oestrogen -> gonadotrophins (testosterone and oestradiol) are responsible of secondary sexual characteristics.

Question 13

Hormonal control of sexual behaviour?

Answer 13

Hormones not only control sexual development, but also interact directly with the nervous system to affect sexual behaviour -> E.g., hormones control the female reproductive cycle: the menstrual cycle. (oestrous cycle in non-primate mammals).
Menstrual cycle -> Follicle stimulating hormone (FSH) -> oestradiol -> Luteinising hormone (LH) -> ovulation -> oestradiol + progesterone (from corpus luteum) -> strengthening walls of uterus.
In non-primate females, sexual behaviour is linked to ovulation. Primate females can mate at any time during their menstrual cycle.

Question 14

Hormones + Sexual Behaviour in Male Rodents

Answer 14

Male rodents’ sexual behaviour: mounts, intromission, and ejaculation -> Depends on testosterone levels: castrated male rats injected with testosterone reinstate sexual behaviour.

Question 15

Hormones and Sexual Behaviour in female rodents

Answer 15

Sexual behaviour in female rodents: lordosis (bending position) -> The female initiates copulation. Only when fertile and ovulating. When receptive, it will approach the male -> Sexual behaviour depends on oestradiol and progesterone. Ovariectomised rats (ovaries removed) display no sexual behaviour -> ER: oestradiol receptor. ER -/-: ER knockout rats (knockout rats are when particular genes are removed – oestradiol). Females with no oestradiol have no receptivity whatsoever.
Similar effects with progesterone receptor KO females.

Question 16

Neural control of sexual behaviour

Answer 16

Retro-tracing to define the circuit that control sexual organs (e.g., Marson & Murphy, 2006) -> Injection of pseudorabies virus (retrograde tracing) in sexual organs (penis, vagina, clitoris) -> Activation of Fos, a marker of neuronal activity, in key brain regions -> Identify of neurons containing sex hormone receptors -> oestrogen and progesterone or testosterone. Looking for specific brain function regions.

Question 17

Spinal mechanisms in men

Answer 17

Men with complete spinal cord transection above the 10th thoracic segment can ejaculate -> A group of neurons in the lumbar region (spinal ejaculation generator) lumbar spinothalamic (LSt) cells control ejaculation -> Destruction of LSt cells in rats abolishes ejaculation, without affecting mounts or intromissions. Brain mechanisms -> excite or inhibit spinal circuit.

Question 18

What is the medial pre-optic area?

Answer 18

rostral to the hypothalamus -> destruction of this abolishes sexual behaviour -> prenatal stress reduces size of sexually dimorphic nucleus decreasing sexual behaviour -> mating causes production of Fos protein (satisfaction and pleasure) -> injection of testosterone enhances sexual behaviour of castrated rats. in males.

Question 19

What is the Medial Amygdala?

Answer 19

destruction disrupts sexual behaviour -> mating causes production of Fos protein. in males.

Question 20

What is Periaqueductal Gray Matter?

Answer 20

normally excites the nPGi -> inhibited by the MPA. in males.

Question 21

What is the central tegmental field?

Answer 21

mating causes production of Fos protein. Inhibited by MPA. in males

Question 22

Nucleus Paragigantocallularis?

Answer 22

(nPGi of medulla) -> normally inhibits mating behaviour, inhibited by the MPA. in males

Question 23

What is sexually dimorphic nucleus (SDN)?

Answer 23

3-7 times larger in male rats than females -> larger in human males than females -> involved in gender identity -> lesions to SDN decrease masculine sexual behaviour. in males

Question 24

Neural control of sexual behaviour - females

Answer 24

Contrary to males, females do not have a spinal circuit controlling sexual behaviour.

Question 25

Ventromedial nucleus of hypothalamus (VMH)?

Answer 25

in females. causes lordosis -> neurons contain oestrogen and progesterone receptors -> enhances sexual behaviour -> destruction abolishes sexual behaviour.

Question 26

What is the medial amygdala?

Answer 26

mating causes production of Fos protein, neurons contain oestrogens and progesterone receptors. in females.

Question 27

What is periaqueductal gray matter?

Answer 27

oestradiol treatment or stimulation of VMH increases neuronal activity -> neurons contain oestrogen and progesterone receptors. in females

Question 28

What is parental behaviour?

Answer 28

Most mammalian species show parental behaviour -> Hormonal and neuronal control, mostly based on data from rodents -> Most research on maternal behaviour -> mice/rats’ pups at birth who are blind, do not regulate their own temperature, cannot release urine and faeces -> nest building is one of the first maternal behaviours during gestation.

Question 29

What is maternal behaviour?

Answer 29

Birth assistance by pulling the pups gently -> nursing -> periodical licks pup’s anogenital region to stimulate urination and defection -> pups’ retrieval if they leave or are removed from the nest -> maternal behaviour is influenced by prenatal hormones, but passage of pups through birth canal also helps.
Hormones can influence maternal behaviour but do not control it -> i.e. progesterone, the main pregnancy hormone, can facilitate nest building. But nest building continues after birth, when progesterone is significantly lower.

Question 30

Medial pre-optic area for maternal behaviour

Answer 30

Medial preoptic area (MPA; involved in male sexual behaviour) is crucial for maternal behaviour -> The VTA -NAC pathway, involved in the reward system, is also necessary for maternal behaviour. It is activated when mothers encounter pups -> Encountering pups is more rewarding than cocaine in lactating females (Ferris et al., 2005) -> Human mothers show activation of the reward system when presented with pictures of their babies (Bartels & Zeki, 2004).

Question 31

Paternal Behaviour in voles

Answer 31

A few mammalian species show paternal care for the offspring -> Monogamous prairie voles share offspring care, whereas polygamous male meadow voles leave the female after mating -> Size of MPA is less sexually dimorphic in prairie voles than in meadow voles -> MPA lesions disrupt paternal behaviour in rats and prairie voles. MPA is also involved in paternal behaviour.

Question 32

What is affiliative behaviour?

Answer 32

Positive social behaviours within the same or different species -> can involve individuals of the same or different sex -> formation of pair bonds in voles (animal) -> prosocial behaviours in humans -> the neuropeptides oxytocin (OXT) and vasopressin (VP) are key for complex social behaviours.

Question 33

Where are the neuropeptides and vasopressin produced?

Answer 33

Neuropeptides oxytocin (OXT) and vasopressin (VP) are produced in the hypothalamus -> they can be released from the posterior pituitary glands as hormones -> or from axons projecting to specific brain regions, as a neuromodulator or a neurotransmitter.

Question 34

How many mammals are monogamous?

Answer 34

3-5% of mammals are monogamous -> explain in humans and other species -> biparental species -> males and females raise the young.

Question 35

Prairie voles and meadow voles differences

Answer 35

Prairie voles: monogamous – bond for life.
Meadow voles: polygamous or promiscuous – male leaves the female after mating. These rodents have been extensively studied them to identify the neurobiological bases of affiliative social responses.

Question 36

Hormones influencing pair bonding study

Answer 36

Exposure to a partner while injected with VP or OXT increased the preference for that partner -> Male and female paired for 1h. One of them receives intraventricular administration of OXT or VP. Then animals are submitted to a partner preference test (180 min) where they can choose to spend time alone, with a stranger, or with the partner they were exposed during drug administration.
Pair bonding is associated with the density of VP receptors in the rewards areas of the brain -> after mating and cohabiting with a female, a male prairie vole tended to spend significantly more time in contact with the preference partner (open columns).

Question 37

Oxytocin receptors role

Answer 37

OXT receptors are highly expressed in PFC and Nacc in prairie voles. prefrontal cortex (PFC) -> nucleus accumbens (Nacc) -> lateral septum (LS) -> ventral pallidum (VP). Partner preference in prairie voles is disrupted after blocking OXT or VP receptors.

Question 38

Promiscuous to monogamous?

Answer 38

Overexpression of vasopressin receptor in the ventral pallidum (V1aR-vp) enhanced mate preference in meadow voles. Vasopressin is a ‘possession gene’.

Question 39

Formation of pair-bonds in humans

Answer 39

Oxytocin and vasopressin seem to influence pair bonding in humans too, but manipulating these carry ethical concerns, so we do not know for sure.
OXT intra-nasal (inhaling through nose oxytocin) caused relaxation and anxiety reduction in humans -> maternal and romantic love activated regions of the brain being rich in vasopressin and oxytocin receptors.

Question 40

Prosocial behaviour

Answer 40

Associated with a wide range of positive social behaviours -> including trust, cooperation, care, empathy, and altruism -> all of which are key for forming and maintaining adaptive human social relationships.

Question 41

Roles of oxytocin in prosocial behaviour

Answer 41

Administration of oxytocin has subtle effects in social behaviours in humans -> trust, empath, social approach, altruism -> oxytocin has effects on brain regions related to reward and fear related to processing -> growing interest in translating oxytocin administration for the treatment of psychiatric conditions ranging from anxiety disorders to autism spectrum disorder -> oxytocin effects on behaviour are highly influenced by individual and contextual conditions.

Question 42

Oxytocin and altruism

Answer 42

Altruism -> Altruism: non-reciprocal prosocial acts which are aimed at improving the welfare of another individual at a personal cost to the altruist.

Question 43

Oxytocin and altruism experiment 1

Answer 43

Experiment 1 -> Saliva samples to measure internal OXT -> Participants received 10 €1 coins -> Social or environmental donation task -> found positive correlation between OXT levels and social donation -> no effect in the ecological frame.

Question 44

oxytocin and altruism experiment 2

Answer 44

Experiment 2 -> OXT intranasal -> Participants received 10 €1 coins -> Social or environmental donation task -> OXT administration increased donations in the social frame, but decreased those in the ecological frame.

Question 45

Oxytocin and empathy

Answer 45

Empathy: cognitive (recognizing emotional states in others) or emotional (sharing experiences of emotional states perceived in others)
Experiment 1 -> OXT or placebo, intranasal -> 45’ later, “Multifaceted Empathy Test” (MET) -> found OXT administration increased empathy ratings in all dimensions.

Question 46

Oxytocin and social approach

Answer 46

Approach behaviour to others was measured after intranasal OXT in women.
Experiment 1 -> OXT or placebo, intranasal -> 45’ later, Stop Distance Paradigm with female or male experimenters -> OXT administration decreased the social distance that female participants kept between themselves and an unfamiliar friendly (and attractive) male experimenter.

Question 47

Role of oxytocin in prosocial behaviour

Answer 47

The involvement of oxytocin in prosocial behaviour seems to be more complex than simply increasing one dimension specifically -> Expression of OXT and OXT receptor maps into areas involved in anticipatory, appetitive, and aversive cognitive states.