Lecture 7 – Parental Behaviour

Vedran Lovic

Term Test 1

Vedran’s office hours: Thursday, Nov. 4 (10-12) and Tuesday, Nov. 9 (2-3).

Lecture Outline

What is parental behaviour? Rat model

Hormones Experience Reward Neural circuitry of maternal behaviour Ontogeny and maternal behaviour

Human maternal behaviour Sensory changes in new mothers Hormones Ontogeny

What is Parental Behavior and Why are Interested in It?

Parental Behavior - any behavior toward a reproductively immature organism that increases the likelihood that the immature individual will survive to maturity. Evidence suggests that early life environment (parental

care) is important for development 30% of mothers who were abused , abuse their own

babies 5% who were not abused, abuse their own babies

(Knutson, 1995) Sensitive mother - securely-attached infant (Goldberg) Securely-attached infant--- relationally -secure adult

(Waters et al., 2000)

Why are animals parental?

Ultimate reasons: passing on genes

Proximal reasons: protection nutrition temperature regulation shelter learning (instincts)

Maternal vs. Paternal vs. Biparental

Environmental demands have played a role in determining parental styles

Maternal Behavior – mothers Paternal Behavior – fathers Biparental – both parents Alloparenting - parenting given by

individuals that are not the biological mother or father

PATERNAL BEHAVIOUR

reversed roles: highly advanced paternal care

examples: pipefish seahorse stickleback fish

BI-PARENTAL CARE both parents contribute

to raising the offspring

examples: penguins ring doves California mice voles Marmoset monkeys Humans

Differences Between Species in the Amount of Care Provided

Three Different Types of Maternal Care in Eutheriean Mammals (based on the type of offspring)

Precocial Born at an advanced stage of

development Little or no help is required for

survival ex. lambs, other ungluates Hider-type vs. follower-type

Altricial Born at an early stage of

development. Helpless require substantial

parental care to survive ex. Dogs, rats, rabbits

Third type - can also be semi-precocial/semi-altricial; ex. Humans and other primates.

Description of Rat Maternal Behaviour

Nest building Pup retrieval Pup licking Nursing postures Normally these behaviors

are evident soon after parturition

Rats that have never given birth (nulliparious or virgins) do not show these behaviors

The Onset of Maternal BehaviorHIGH

LOW

Virgin / onset of pregnancy

Day 16

parturition

Parabiotic Preparation

preparation where blood is exchanged between a rat that was maternal and a rat that was not maternal

Soon after virgin rat will show maternal behavior

Conclusion: blood-borne factor is important in the induction of maternal behavior in rats

Pregnancy and Parturitional Endocrine Profile

Latency to Become Maternal After Hormonal Treatment

0

2

4

6

8

10

Estrogen andprogesterone

Progesterone Control-vehicle

Hormone Treatment

LA

TE

NC

Y I

N D

AY

S (

med

ian

)

-+ -

Bridges,1984

Maternal Behavior - Hormones

other hormones: prolactin: milk production (infusion into MPOA

can induce maternal behavior rapidly) oxytocin: uterine contractions & milk letdown

(central administration can induce maternal behavior rapidly)

opioids & endorphins: reduction of pain associated with parturition

Other Hormones

Other Hormones – Glucocorticoids (Corticosterone)

0

20

40

60

80

100

120

140

160

0ug 25ug 100ug 300ug

CORTICOSTERONE (ug/ml)

Dur

atio

n (m

ean

sec)

Corticosterone (moderate levels) facilitates maternal pup licking in rats

Maternal ResponsivenessHIGH

LOW

Virgin / onset pregnancy

Day 16

parturition

P E CORT OXY PRL

Postpartum Experience

Soon after the parturition the hormones that initiated the onset of maternal behavior begin to decrease

So what maintains the maternal responsiveness? Can experience with pups maintain maternal

responsiveness? Non-partum multiparous female rats are responsive to

young pups How much experience is necessary so that rats are

maternal responsive in the absence of hormones?

PARADIGM TO ASSESS MATERNAL EXPERIENCE

EXPOSUREPHASE

Experience orNo experience

separationTESTINGPHASEretentiontesting

Latency to respond maternally to pups

Parturition

0.5h, 1h, 2h, 24h

10 days

Learning to Maternal – Maternal Memory (Rats need about 30 min of interaction with pups to acquire the experience)

0

1

2

3

4

5

6

7

8

INEXP 3 min-retonly

EXP-1/2 hr EXP-2 hr EXP-24 hr

Duration of Experience

Lat

ency

to

Bec

ome

Mat

erna

l

Orpen & Fleming, 1987

Maternal Experience Effect

Maternal Experience Effect: A brief interactive experience with pups post-partum sustains maternal responsiveness throughout lactation and beyond (at least 30 min).

Mother has to be interacting with pups in order to acquire this experience.

Seeing, smelling and hearing the pups is not enough (if pups are placed in perforated Plexiglas box)

Cyclohexemide (protein synthesis inhibitors) injections soon after maternal experience block the maternal experience effect (prevents cosolidation)(Li & Fleming, 2004)

Lesions of nucleus accumbens will also prevent consolidation (Li & Fleming, 2004)

Pups Are Rewarding to New Mothers

Mothers will bar press for pups, whereas virgin rats will not

Rewarding properties of pups can be blocked with administration of dopamine antagonists

Like other motivated behavior, maternal behavior is dependent on the hypothalamus

Specifically, medial preoptic area (MPOA) of the hypothalamus is the most important nucleus for maternal behavior

Lesions of MPOA will abolish maternal behavior

Neural Circuitry of Maternal Behavior

Neural Circuitry of Maternal Behavior

Cortical lesions do not significantly impact maternal behavior Amygdala inhibits the activity/behavior produced by the MPOA Multiple sources of evidence: electrolytic lesions destroy all the

tissue (cell bodies and axons) What could a problem with concluding that MPOA is the brain area

for maternal behavior? The excitotoxic lesions – N-methyl-DL-aspartic acid (NMA)

Further Evidence for Involvement of MPOA in Maternal Behavior

Looking at activation of brain areas (cells) associated with maternal behavior

Looking at activation looking at expression of proteins produced by immediate early genes (IEG) (e.g., c-fos gene produces protein called Fos)

Fos protein peaks 1-2 after cells have been active

Immunohistochemisty (IHC) – labeling Fos protein using antibodies

Typical Fos Study

1. Let the animal engage in a particular behavior2. 90 min later sacrifice the animal 3. Perform IHC and look for expression of Fos4. Control conditions involve control animals being

exposed to all the same conditions except the behavior of interest

5. Use subtractive technique (activation in experimental brain – activation in control brain = brain activation associated with behavior of interest).

Post-partum Maternal Experience is Associated with Fos Expression In Response To Distal Pup Cues or Pup-associated Cues in MPOA

Day 1: experienced pp rats were exposed to pups (p) box(b) ,cage (c) for two hours; inexperienced animals were not

Day 10: animals exposed to pups in a box in new cage (pbc), box in cage (bc) or home (h) for 2 hours

Animals sacrificed for c-fos icc Fleming & Korsmit, 1996

MPOA has receptors of hormones thought to be involved in maternal behavior

Neural Circuitry of Maternal Behavior

Sensory Control of Maternal Behavior

Sensory stimuli from pups (touch and smell in particular) are important for maternal behavior

Fos studies show activation in somatosensory cortex in maternal rats

Removal of olfactory bulbs reduces maternal licking in postpartum rats

Sensitization of Virgin Rats Initially virgin rats avoid pups Might show aggression / cannibalize pups However, if virgin rats are exposed to pups for days they will

eventually show maternal behavior (sensitization) Why might this be the case? Neophobia – fear of new things (pups sight, smell) Olfactory bulb removal facilitates sensitization process in virgin

rats (or infusion of ZnSO4) Amygdala lesions also facilitate maternal behavior in virgins If virgins are neophobic, does that mean that new mothers are

less neophobic? Yes, less fearful of novel envioronments, food etc.

Ontogeny – Early Life Experiences with One’s Own Mother

There a positive correlation between the maternal “style” of mother rats and the maternal “style” of their daughters

Genetics or experience?

R2 = 0.262

0

50

100

150

200

250

300

350

0 100 200 300 400

Mothers (time in sec)

Dau

ghte

rs (

Tim

e in

sec

)

Artificial Rearing

ARTIFICIALLY-REARED (AR) and MOTHER-REARED (MR) GROUPS

•AR (MIN)- AR, with two AGL strokings (days 4-16)•AR (MAX)-AR, 8 dorsal•MR (sham)- AR sham surgery•MR (intact)-MR

AR PUPS, RAISED WITHOUT MOTHERS, SHOW DEFICITS IN ADULT MATERNAL BEHAVIOR MATERNAL-LIKE LICKING STIMULATION REVERSES THESE EFFECTS

BODY-LICK GENITAL-LICK CROUCH-OVER NEST-BUILD RETRIEVE 0

20

40

60

80

100

120AR-MIN (DEPRIVED)

AR-MAX (DEPRIVED)

MR (NON-DEPRIVED)

*#

#

* *

*

*

*#

#

Artificial-Rearing Reduces Fos in Response to Pups in MPOA - Replacement ‘stroking’ reverses some of these effects

AR-MIN AR-MAX MR0

50

100

150

200

250

300

350

400

NU

MB

ER

OF

CE

LL

S

*

*

Gonzalez et al. in prep

Maternal Behavior in Humans

Many cultural differences – no clear set of maternal behaviors

Affectionate behaviors: patting, cuddling and kissing etc.

Instrumental behaviors: changing diapers, changing the clothing and burping the infant etc.

Sensory Changes in New Mothers

Compared to non-mothers, new mothers find odors associated with infants more pleasing (or less aversive): general body odor, urine and feces

New mothers are good at identifying the odor, cries and tactile features of their infant

Cry Study: Affect (VAS) and Heart-rate Responses to Infant Cries and Control stimuli

Heart-rate monitor

cry stimuliVAS

y = 0.0706x + 2.5861

0

2

4

6

8

10

12

14

0 20 40 60 80 100 120

SYMPATHY RATING (VAS)

SAL

IVA

RY

C

OR

TIS

OL

(nM

ol/L

)

Maternal Behavior in Humans – Hormones: Cortisol

Mothers with a positive shift in the ratio of estradiol to progesterone (i.e., the ratio increases) show more positive attachment to their infants than mothers whose pregnancy endocrine profile shows a negative shift (or no change)

Maternal Behavior in Humans – Hormones: Estradiol and Progesterone

0

50

100

150

200

AFFECT CARETAKE

TIM

E (m

ean

sec+

se )

CONSISTENT

NON-CONSISTENT

20.4

Mothers Who Received Continuous Care by at Least One Caregiver Prior to Age 12 Show More Affectionate Touching but less Instrumental Touching with their Infants

Maternal Behavior in Humans – Ontogeny

Some Questions To Think About: What is the role of hormones in rat maternal

behavior? What maintains the maternal behavior in the rat? What is the evidence for the involvement of

particular brain structures in maternal behavior? What is the role of early life environment? What is the role of hormones in human maternal

behavior? What is the the role of early life environment in

human maternal behavior?