Panksepp – Nurturance in mammals arose from neurochemical processes that controlled
egg-laying and mating behavior in reptiles. Vasotocin (precursor to oxytocin) controls
sexual urges in reptiles and helps to deliver young reptiles
In mammals, vasotocin evolved into oxytocin and argine-vasopressin (AVP), which are
important in mating behavior. They differ from vasotocin by one amino acid.
Panskepp- Oxytocin promotes receptivity in female mammals (lordosis effect in rats) and
also prepares the mother’s brain for nurturance. Initial clue was that blood transfused
from a rat, which had just given birth, could instigate maternal behavior in a virgin rat.
Heightened maternal desire corresponds to the peak of hormonal change, reaching the
apex several hours before birth (during this time, rat moms build nests).
Estrogen (moderate during pregnancy) rapidly increases as birth nears
Progesterone (high during pregnancy) plummets as birth nears
Increase in prolactin, inducing mom’s acinar glandular tissues to produce milk.
Prolactin is important in keeping natural behavior .Brain injections of prolactin promotes
nurturance and females who are non-maternal (because of removal or pituitary gland)
become maternal when prolactin is provided
Increase in oxytocin receptors during the last days of pregnancy and during the first few
days of lactation as well as an increase in the hypothalamic neurons that make oxytocin.
During lactation, oxytocin cells communicate with each other via gap junctions between
oxytocinergic neurons, synchronizing the message.
The greatest oxytocin receptor proliferation is observed in the bed nucleus of the stria
terminalis (BNST). When it is damaged, maternal behavior is impaired.
The stria terminalis is a bundle of nerve fibers that passes from the amygdala along the
boundary between the thalamus and caudate nucleus mostly to the anterior part of the
hypothalamus with a few fibers crossing the anterior commissure to the amygdala on the
Lesions of the BNST and nearby preoptic area (POA) can eliminate maternal behavior