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Lecture 5

Lecture 5 - Parental Behavior

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University of Toronto Mississauga
Emis Akbari

PSY398H5S – Motivational Systems Lecture 5 – January 31, 2013 Parental Behavior Introduction •any behavior contributing to survival of offspring •by male – paternal behavior •by female – maternal behavior •as critical a reproductive behavior as copulation •extremely variable by species •fish – no parental care •mammals – very high parental care In mammals, varies by offspring development •monotremes (platypus) – lay eggs •marsupials (kangaroo) – embryonic at birth •eutherian mammals (“true” mammals) – 3 patterns Eutherian mammals: 1) Altricial young – underdeveloped at birth •mom spends lot of time with •rats, dogs, cats 2) Precocial young – relatively well-developed •mom infrequently visits, interact only to nurse •hoofed animals (deer, sheep, goats) •two types of maternal care •hider-type – mom hides them, later they follow •follower-type – offspring follow mom from birth •exclusive mother-infant bonds formed Eutherian mammals: 3) Semi-precocial young – in between •relatively helpless, but can cling •some thermoregulation •primates Components of Prenatal Care •direct parental care •carrying, cleaning, nursing •indirect parental care •nest building, protection, gathering food Sex Differences in Parental Behavior •With the exception of most bird and some fish species, paternal behavior is rather rare in the animal kingdom; maternal care is much more common •Why is there a sex difference? •Two sexes produce different gametes •Sperm vs. eggs •Reproductive success PSY398H5S – Motivational Systems Lecture 5 – January 31, 2013 •Reproductive Effort: •1) mating effort - males concentrate effort here – locating & fertilizing as many different females as possible is the best way for males to achieve maximal reproductive success •2) parental effort – females concentrate their effort here – because each offspring represents a substantial proportion of a female’s lifetime investment of time •Consider human female: •9 months – gestation •1-2 years lactation •Males can potentially fertilize hundreds of women in this time •Parental behavior is thought to have evolved when fertilized eggs did not develop, hatch and result in the survival of the young. •Species that exhibit parental care produce fewer young
 •Young develop more slowly, but are more likely to survive to reproductive age with parental care.
 •Hormonal basis of parental behavior is most highly evolved in the true mammals. Pups are Rewarding to New Mothers • Motherswillbarpressfor pups, whereas virgin rats will not • Rewardingpropertiesof pups can be blocked with administration of dopamine antagonists Hormonal Control of Maternal Behaviour So what are the differences between virgins and lactating rats? Parabiotic studies (1960s-70s) •circulatory systems conjoined •virgins connected to pregnant/lactating females •evidence that blood-born factors involved 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 Hormonal Control of Maternal Behavior  Pituitary PRL inhibitor (ergocornine) during late pregnancy does not inhibit onset of maternal behavior Is PRL needed or not?!? •yes, it is •PRL from pituitary not needed...another source? •PRL from PLACENTA •placental lactogens: These hormones are molecular relatives of prolactin and growth hormones. These hormones have been identified in primates and rodents, but not in other species •in pregnant females, inhibiting pituitary PRL does not stop placental lactogens Oxytocin: controversial if has a role or not •some show it facilitates maternal behavior PSY398H5S – Motivational Systems Lecture 5 – January 31, 2013 in E+P virgins •OT antagonist delays MB in E+P virgins •OT antagonist at birth temporarily impairs •others can’t show this •OT-knockouts normal •testing procedure? •virgins put in test cage 1-2 hr before testing, OT facilitates maternal behavior •virgins put in test cage 1 week before, or tested in home cage, no OT effects •OT effects may require recent stress Maintenance of Maternal Behaviour  After parturition, remove ovaries, adrenals, pituitary  •maternal behavior still normal and continues  •within 5 days, all hormones back to virgin levels  •apparently little role for hormones in maintenance  •doesn’t maintain if pups removed after parturition Postpartum Experience  •Soonaftertheparturitionthehormonesthatinitiatedtheonset of maternal behavior begin to decrease  • So what maintains the maternal responsiveness?  • Can experience with pups maintain maternal responsiveness?  • Non-partummultiparousfemaleratsareresponsivetoyoung pups • How much experience is necessary so that rats are maternally responsive in the absence of hormones? Maternal Experience Effect •MaternalExperienceEffect:Abriefinteractiveexperiencewithpupspost- 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 •Cyclohexemide(proteinsynthesisinhibitors)injectionssoonaftermaternal experience block the maternal experience effect (prevents consolidation) – therefore this makes it similar to other forms of learning •LesionsofNucleusAccumbenswillalsopreventconsolidation–siteofmaternal memory? Maintenance of Maternal Behaviour  What cues do dams need from pups for maintenance? o •somatosensory o •dams mystacial pads and/or ventrum anesthetized o •if both anesthetized, no retention o •if either singly anesthetized, full retention Sensory Control of Maternal Behaviour  Once maternal behavior established, what cues does mom need? •visual – maternal behavior not affected by blinding  •auditory – maternal behaviour not much affected by deafening  Once maternal behavior established, what cues does mom need? o •visual – maternal behavior not much affected by blinding o •auditory – maternal behaviour not much affected by deafening o •taste – mothers not much affected by anesthetizing tongue PSY398H5S – Motivational Systems Lecture 5 – January 31, 2013 o •smell – inhibits maternal behaviour  Olfaction and Maternal Behavior o •pup odours aversive to virgin females o •become attractive during late pregnancy  •what if remove olfactory inputs in virgin rats? •Facilitates onset of maternal responding Sensory Control of Maternal Beha
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