Front Matter

Development of Oxytocin and AVP Neurons in Various Animals and in Man 103

Numerous studies have shown that children with autism have significantly
lower levels of plasma oxytocin and AVP than their peers [8,20,45]. A recent
study also illustrated that mothers of ASD children show low levels of oxytocin
and AVP and high levels of testosterone. Furthermore, lower concentrations of
oxytocin in plasma are associated with lower social and cognitive functioning
in children.

Development of Oxytocin and AVP Neurons

in Various Animals and in Man

In many species  –  from zebrafish to Homo sapiens  –  oxytocin producing
neurons emerge from the proliferative (“convoluted”) neuroepithelium of the
diamond shaped third ventricle during fetal development [64–66]. In the
hypothalamus, oxytocin is produced in the specialized secretory cells called
magnocellular neurons. Birth‐dating studies have discovered that the hypotha-
lamic neurons that subsequently produce oxytocin are generated in the second
half of the gestational period in rodents, within the first quarter of the gesta-
tional period (E30–43; length of pregnancy ~165 days) in macaques [10], and
in the middle of pregnancy in humans [10]. In humans, the supraoptic and

Supra-optic

nucleus

Paraventricular

nucleus

Hypothalamo-

hypophysial tract

Inferior

hypophysial

artery

Optic

chiasma

Vasopressin

oxytocin

Figure 4.3 Illustration of the major neurons that produce oxytocin and AVP. Oxytocin is
mainly synthesized in the paraventricular hypothalamic nucleus and supraoptic nucleus,
stored in Herring bodies and released into systemic circulation from the posterior pituitary.
In the pituitary gland, oxytocin is packaged in large, dense‐core vesicles, where it is bound
to a large peptide fragment called neurophysin I.