Modules 1.1-1.4 Reproductive Behaviour and Libido

Question 1

Which region of the hypothalamus regulates sex drive/libido?

Answer 1

The Medial Preoptic Area (MPOA) of the Anterior hypothalamus

Question 2

The medial preoptic area is one source of what hormone?

Answer 2

The medial preoptic area is one source of GnRH (which stimulates sex steroid production)

Question 3

Which regions of the hypothalamus have high numbers of androgen and estrogen receptors?

Answer 3

The hypothalamic region as well as the ventromedial nucleus

• ties into the integration of reproductive function in which GnRH acts to eventually support gonadal function including production of sex hormones which can then act on multiple sites in the brain (including the MPOA)

Question 4

How was the median-preoptic region (MPOA) discovered as a mediator of sex drive?

Answer 4

Lesion of the MPOA which lead to disrupted sexual behaviour

Disrupted Appetitive behaviours

• Solicitation - females
• timing and spacing of Lordosis - females (exaggerated curvature of the spine)
• Sexually rewarded maze learning in males
  
  • if male successfully completes maze they can mate
  • viewed as analogous to desire in humans

Question 5

Which behaviours were disrupted by lesion of the medial preoptic area?

Answer 5

Disrupted Appetitive behaviours

• Solicitation - females
• timing and spacing of Lordosis - females (exaggerated curvature of the spine)
• Sexually rewarded maze learning in males
• if male successfully completes maze they can mate
  
  • viewed as analogous to desire in humans

Question 6

What is the role of sex hormones in sexual desire/libido?

Answer 6

In both males and females, androgens are associated with increased libido

• eliminated endogenous androgens (castration or ovariectomy) abolishes sexual desire

Question 7

______ hormones act centrally and peripherally to ensure a sexually relevant stimulus is more likely to elicit a sexual response

Answer 7

Steroid hormones act centrally and peripherally to ensure a sexually relevant stimulus is more likely to elicit a sexual response

Question 8

Steroid hormones act ______ and ______ to ensure a sexually relevant stimulus is more likely to elicit a sexual response

Answer 8

Steroid hormones act centrally and peripherally to ensure a sexually relevant stimulus is more likely to elicit a sexual response

Question 9

Sexual hormones modulate _________ release

Answer 9

Sexual hormones modulate central neurotransmitter release

• Especially dopamine
  
  • highly implicated in both male and female sexual behaviour

Question 10

Sex hormones stimulate _____[neurotransmitter]____ release which has been demonstrated in males and females

Answer 10

Sex hormones stimulate central dopamine release which has been demonstrated in males and females

Question 11

Central dopamine release occurs in the ________ of the hypothalamus

Answer 11

Central dopamine release occurs in the MPOA (medial preoptic area) of the hypothalamus

• Recall: region features numerous neurons responsive to androgens and estrogens

Question 12

Sex hormones bind to receptors in the ___[region of hypothalamus]__ and trigger _____

Answer 12

Sex hormones bind to receptors in the MPOA and trigger dopamine release and facilitation of the sex drive

Sex hormones are thought to prime sensory processing in the brain to be receptive to sexually relevant stimuli

Question 13

How are sex hormones are thought to prime sensory processing in the brain

Answer 13

Sex hormones are thought to prime sensory processing in the brain to be receptive to sexually relevant stimuli

Question 14

What happens if dopamine signalling in the MPOA is disrupted (eg you inject a dopamine antagonist into the MPOA)

Answer 14

• Decrease in sexual motivation

Question 15

What does measuring dopamine levels during pre-copulation show? What does this indicate?

Answer 15

Dopamine in MPOA rises in the pre-copulatory period in male and female rats indicating a role in sexual motivation

• psychiatric disorders that disrupt central dopamine signalling are often associated with low libido and in some cases sexual dysfuntion

Question 16

Attraction is primarily associated with _______ and ________

Answer 16

Attraction is primarily associated with catecholamines and dopamine signaling in the brain

Question 17

Romantic attraction is associated with:

Answer 17

• Increased monoamine NT’s
  
  • dopamine, norepinephrine (derived from DA)
  • In the mesolimbic (reward centres) of the brain

Question 18

Results of increased central dopamine? (2)

Answer 18

• Euphoria, loss of appetite, hyperactivity, increased mental activity, decreased need for sleep
• Heightened motivation and goal-directed behavior
  
  • Increased dopamine is likely associated with increased passionate attraction in humans

Question 19

Attachment is associated primarily with _____ and _____

Answer 19

Attachment is associated primarily with vasopressin and oxytocin

Question 20

Vasopressin and oxytocin are peptides released in the ____ and produce _____

Answer 20

Vasopressin and oxytocin are peptides released in the CNS and produce produce monogamous male-female attachment and monogamous parenting behaviour

Question 21

From a neuroscientist point of view, attachment is thought to depend on ________; why?

Answer 21

From a neuroscientist point of view, attachment is thought to depend on sexual intercourse (consummatory actions)

• It’s upon copulation that vasopressin and oxytocin are released in the brain thus facilitating development of attachment
• Not necessarily true in humans

Question 22

Which hormone facilitates the pair bond in males? Females? (prairie voles)

Answer 22

Males - vasopressin

Females - oxytocin

Question 23

Where do the hormones vasopressin and oxytocin act in the brain?

Answer 23

• Oxytocin receptors are rich in nucleus accumbens and prefrontal cortex​
• Vasopressin receptors in ventral pallidum
• Areas included in the central reward circuits

Question 24

How are oxytocin and vasopressin related to human attachment?

Answer 24

• Increased oxytocin release following orgasm
• Increased vasopressin release during sexual arousal in males
• Sex may not be essential for bond formation but may be facilitative (ie may play a permissive role)