Role of OT in Maternal Behavior

Role of OT in Maternal
Behavior
by Nicholas Korniczky

Young et al. Claim
"OT, both in the periphery and brain, also
plays an important role in behaviors
associated with maternal care, including
uterine contraction at parturition, milk
ejection during lactation and the regulation
of maternal behavior in females."

Terms:
parturition: childbirth
anxiolytic: related to feelings of anxiety
peripartum period: occurring during the last month of
gestation or the first few months after delivery, with
reference to the mother
dams: the female parent of an animal

Oxytocin
Oxytocin that is secreted into the systemic circulation is
produced by about 9000 magnocellular neurons, many of
which are aggregated in two hypothalamic nuclei:
• supraoptic nucleus (SON)
• paraventricular nucleus (PVN)
Effects:
• suppress appetite
• stimulates male sexual arousal, female sexual receptivity
• grooming behavior
• is antianxiolytic (increases anxiety)

OT/AVP released independently
during parturition
• Once thought that they were both released
together
• However, evidence shows that they are released
indepently because their rates of release are
different and independant

OT/AVP
Experiment
Note: Lower bar represents OT/
VP being depleted.
Taken from:
Pituitary oxytocin and vasopressin content of pregnant rats
before, during and after parturition. [Endocrinology. 1971]

Milk Ejection Reflex
• When a lactating mammal is suckled by its
young, the magnocellular neurons fire
intermittently in brief, intense bursts of action
potentials, each of which triggers oxytocin
release
• Why Oxytocin in IMPORTANT: lactation can be
blocked by small amounts of oxytocin antagonist
injected into the SON (supraoptic nucleus)
o large amount of OT release will counteract
this

OT Animal Variations: Sheep vs.
Rats
• An ewe is able to recognize her own lamb from the
moment it is born, and she feeds it alone.
• This involves an ‘olfactory memory’ of the lamb that is
fixed by neural pathways activated at parturition by
centrally released oxytocin
• Virgin and early pregnant rats typically avoid contact
with newborn pups, but at the end of pregnancy, when
the neural circuits regulating maternal behavior are
established, rats lose this apprehension.

Sheep vs. Rats (cont.)
• 'Motherhood' changes the
neuroendocrine response
o Now oxytocin will release into the blood and
hypothalamus following emotional, physical,
or pharmacological stressors that are
attenuated in the peripartum period

Maternal Aggression
• Levels of aggression are linked to anxiety
o rats selectively bred for high anxiety-related
behavior (HAB) are more aggressive than rats bred
•
for low anxiety-related behavior (LAB).
Oxytocin release within the PVN and central nucleus of
the amygdala (CeA) is higher in HAB than in LAB dams,
and blockade of OTR by bilateral infusion of an OTR
antagonist directly into the PVN or CeA reduced
aggression in HAB dams, whereas infusion of synthetic
oxytocin into the PVN in LAB dams tended to increase
maternal aggression

Possible Adaptations
• Possibly in anticipation of parturition in late
pregnancy, oxytocin neurons become less sensitive
to stressful stimuli and to hyperosmotic stimuli.
• This hyporesponsiveness may be important to
allow pituitary stores of oxytocin to accumulate in
expectation of the large demand for oxytocin
during parturition and lactation, and to reduce the
risk of premature delivery.

Other thoughts/Possible
Implications
• The extent to which changes are adaptations to
facilitate the influence of oxytocin or which are
consequences of increased activity in the systems.
• However, the potential ability of oxytocin to ‘reprogramme’
its neural targets by altering functional
connectivity is an attractive concept for understanding
maternal behavior, but this remains to be tested.

References
87. Fuchs A-R, Saito S. Pituitary oxytocin and vasopressin content of pregnant
rats before, during, and after parturition. Endocrinology. 1971;88:574–578.
[PubMed]
142. Leng G, Meddle SL, Douglas AJ. Oxytocin and the maternal brain. Curr
Opin Pharmacol. 2008;8:731–734. [PubMed]