Lecture 9 (Bechtold)

Question 1

maternal care innate?

Answer 1

Onset of maternal care involves a switch in the valence of pup stimuli, resulting from inhibition of avoidance and activation of approach neural systems in response to infant stimuli.

Question 2

non selective recognition?

Answer 2

A non-selective recognition typically occurs in mothers that give birth to altricial young, lots of young

maternal care is directed toward generic infant stimuli rather than to particular infants, and mothers will care for any conspecific infant throughout the postpartum period.

General infant stimuli are recognized as positive, rather than negative, social stimuli.

Question 3

selective recognition?

Answer 3

A selective recognition operates in mothers that give birth to precocial young (e.g. sheep), or semi-mobile young (e.g. primates)

selective maternal care is ultimately directed toward the particular offspring that the mother gives birth to, while other (alien) young are rejected.

Key role for early olfactory cues in selective offspring recognition

Question 4

what happens if virgin rats are continuously exposed to healthy pups?

Answer 4

maternal behaviour
eventually occurs.

around 7 days (sensitization latency).

will even show nursing behaviour despite not being able to lactate and feed.

mothers can’t show such delay, pups would die of neglect, therefore hormal events occuring at the end of pregnancy must allow for immediate materal responsiveness at parturition.

Question 5

oxytocin injections

Answer 5

oxytocin injections induce maternal behaviour in mice/rats/sheep (dolly aw).
can cause non pregnant females to accept alien lambs.

intracerebroventricular injection to virgin female rats display full maternal behaviour within 1 hour.

Question 6

endocrine rhythms in in oestrus, pregnancy and sex drive

Answer 6

Testosterone = strongest sexual motivation in males and females

Estrogens also increase female sex drive

progesterone alone can inhibit sex drive, but in combination with oestrogen increases female sexual motivation.

fluctuations in progesterone during oestrus can alter pheromone related sensing in VNO and decrease sex drive (same pheromone has dif response at dif point in oestrus cycle)

Question 7

pheromone sensing behaviour throughout mice oestrus cycle?

Answer 7

5 day cycle.
test response to males.
durign oestrust increases attraction, due to VNO response.

Fluctuations in progesterone during oestrous cycle can alter attraction related pheromone sensing in VNO (in mice) decrease sexual motivation.

Question 8

effects of progesterone and oestrogen during pregnancy?

Answer 8

progesterone helps to suppress immune responses of the mother to fetal antigens, which prevents rejection of the fetus

progesterone inhibits uterine contractions

Oestrogens and progesterone stimulate lobular alveolar growth (facilitating milk production). Also drives prolactin production

increasing ratio of estrogen to progesterone makes uterine smooth muscle more sensitive to stimuli that promote contractions (e.g. OT)

Question 9

how do hormones change in the lead up to birth?

Answer 9

huge surge in oestrogens in the lead up to birth, both humans and rats, almost all animals.

humans - Rise in circulating estrogen and progesterone secreted by the ovaries during pregnancy, followed by the precipitous drop in progesterone at the end of pregnancy, signals that parturition is eminent

Question 10

oxytocin in labour?

Answer 10

stimulates contractions, positive feedback which also releases oxytocin in the brain/PVN

Question 11

how to induce maternal behaviour?

Answer 11

sheep?
Vagino-cervical stimulation (VCS) can mimic effects of birth and stimulate maternal behaviour and selective bonding

Diminished with oxytocin antagonist

just as good as oxytocin injections.

Question 12

how is maternal behaviour primed at end of pregnancy and by parturition?

wrt. Oxytocin

Answer 12

High oestrogen/progesterone ratio
OT release into the brain from VCS
OT release stimulated by suckling (again via brainstem relay to PVN)

These actions on the brain stimulate the immediate onset
of maternal behavior at parturition.

BUT once maternal behavior becomes established during the early postpartum hours, enduring attraction between a mother and her infant(s) persists after the hormonal events that activated the behavior have waned
(i.e. independent of hormone signals)

Question 13

Oxytocin during late pregnancy, parturition and maternal (wrt olfactory and reward circuits)

Answer 13

During late pregnancy, receptors for OT are up-regulated in both the brain and the uterus in response to elevated oestrogen levels.

OT synthesized in the hypothalamic neurons, is released into the brain at birth, facilitating olfactory recognition of offspring, aiding parturition and stimulating the onset of maternal care.

The maintenance of maternal behaviour during lactation also involves OT (but also prolactin and dopamine (DA) systems).

Question 14

MPOA

Answer 14

medial preoptic area (MPOA) and the adjoining bed nucleus of the stria terminalis (BST) are essential components of the neural circuitry regulating maternal behavior

MPOA neurons are robustly activated by pup stimuli

OT administration into the MPOA increase maternal behavior in rats

MPOA activity is necessary for maternal behaviour in sensitized virgin rats

MPOA is essential for maternal motivation in ewes as depression of MPOA activity blocks the onset and maintenance of maternal behavior

Question 15

MPOA destruction?

Answer 15

Destruction of the MPOA/BST abolishes maternal care (rats/sheep)

Question 16

inputs to MPOA?

Answer 16

PVN produce oxytocin and send there. PVN primarily responsive to suckling/VCS

stimuli go through amygdala to MPOA.

estradiol stimulates the expression of OT receptors in MPOA.

OT at the MPOA (from PVN activation by VCS and suckling) is essential for the onset of maternal behaviour at parturition in rats

Question 17

MPOA outputs?

Answer 17

DOP OUTPUTS
MPOA –> VTA –> NAc
NMPOA –> PVN —> VTA

Question 18

testing sensitization latency and NAc

Answer 18

rats allowed 1h of postpartum maternal experience and then the pups removed. Immediately after this 1h experience, DA receptor antagonists, an OTR antagonist (OTA), or control solutions were injected into NAs.

Ten days later, females were re-exposed to young foster pups on a daily basis and sensitization latencies for the re-initiation of maternal behavior were recorded.

D1 or D2 blockade increases sensitization latency slightly.

Blockade of both D1 and D2 receptors in NAs effectively disrupted maternal memory, back to virgin state - 7 days.

blockade of OT receptors in NAs also disrupted maternal memory formation.

Question 19

limbic motor integration?

Answer 19

“limbic-motor integration”
VP is a major motor output relay for reward systems

VP GABA inputs from NAc, sits behind NAc.
when dopamine high, inhibits NAc, which lessens inhibition of VP

Question 20

summary of pathways

Answer 20

look up

Question 21

VTA signal in humans when responding to own children

Answer 21

fMRI big ol signalling, same pathways as ratbois.

avoidance areas activate when not own child

Question 22

testosterone human

Answer 22

In many species, testosterone supports mating effort at the

expense of parenting effort.

Question 23

selectivity of mother infant bond

Answer 23

Selective maternal recognition involves neural plasticity within both the olfactory bulbs and the amygdala.

VCS activates norepinephrine (NE) and OT release into the olfactory bulbs, which may influence the particular types of lamb stimuli that are relayed to the amygdala

NE release into the olfactory bulbs is necessary for the development of maternal selectivity

Inhibition of neural communication in the amygdala can disrupt the development of maternal selectivity without interfering with ongoing maternal motivation (Ewes showed maternal behavior toward their own and alien lambs, while control females only cared for their own lamb).

Question 24

testis size

Answer 24

Testes size is also correlated with increased investment in mating, both across and within nonhuman species

In human fathers, testes size has a significant negative correlation with instrumental caregiving. Testes size also has a robust inverse correlation with the VTA activation in response to viewing pictures of one’s own child

Question 25

summary of oxytocin brain regions

Answer 25

Activation of the PVN causes the release of OT
into several different brain regions

OT release into MPOA, VTA, and NAc boosts maternal motivation and attraction to young at parturition.

OT and DA release into NAc promotes the synaptic plasticity within the NAc–VP circuit so that maternal attraction to young persists throughout the postpartum period in the absence of continued pregnancy hormone stimulation.

In species that form selective attachments to particular young, OT action on the olfactory bulbs and amygdala (MeA/CoA) influences the development of selective recognition.