No production or release of FSH and LH effectively inhibits the ovarian cycle
Binds to PRL receptor in breast tissue and stimulates various actions
Stimulus from suckling travels from the breast, through the spinal cord, and to the hypothalamus
Neurons from the spinal cord inhibit neurons of the preoptic area, causing a fall in GnRH production
Neurons from spinal cord stimulate the production and release of oxytocin
Binds to OXTR receptor
During childbirth, binding of oxytocin stimulates uteran contractions
Neurons from spinal cord stimulate the production and release of oxytocin
Action stimulated by oxytocin binding to OXTR receptor
Neurons from the spinal cord inhibit dopamine release
Mother interacts with newborn; psychogenic stimulation or anticipation of feeding/suckling

Hypothalamic Pituitary Axis-Prolactin

Lactating Mother

Breast

Spinal Cord

Arcuate Nucleus

Supraoptic Nucleus

Paraventricular Nucleus

Preoptic Area

Newborn baby's action of suckling begins signal transduction

HYPOTHALAMUS

Posterior Lobe of Pituitary

Oxytocin

c1

Anterior Lobe of Pituitary

Gonadotrophs

Prolactin-releasing lactotrophs

Prolactin

c1

Hypothalmic-portal system

c1

Milk Production

Glandular Tissue Development

Breast Differentiation

Mammary Gland Development

Lactogenic Enzyme Synthesis

Prolactin is produced in the anterior pituitary gland. More specifically, lactotroph cells produce prolactin in the anterior pituitary gland where it is stored and then released into the bloodstream.

Actions stimulated by prolactin binding at PRL receptor

Duct Proliferation & Branching

Oxytocin is originally produced and released from the paraventricular and supraoptic nuclei; however, it travels down through the hypothalamic-portal system and is finally "released" from the posterior lobe of the pituitary.

The hypothalamic portal system allows hypothalamic hormones to be transported to the anterior pituitary without first entering the systemic circulation.

The suckling of a newborn on a mother's breast has four effects. Firstly, it stimulates the sensory nerves, which then carry the signal from the breast to the spinal cord, where these nerves then synapse at the dorsal horn with neurons that carry the signal to the brain. Secondly, in the arcuate nucleus, the sensory afferent input from the nipple inhibits neurons that release dopamine. Dopamine normally travels via the hypothalamic-portal system to the anterior pituitary lobe, where it inhibits prolactin release from lactotrophs. Therefore, inhibition of dopamine release leads to an increase in prolactin release. Thirdly, in the supraoptic and paraventricular nuclei, the sensory afferent input from the nipple triggers the production and release of oxytocin in the posterior pituitary lobe. Fourth, in the preoptic area and arcuate nucleus, the sensory afferent input from the nipple inhibits GnRH release. GnRH normally travels via the hypothalamic-portal system to the anterior pituitary lobe, where it stimulates the synthesis and subsequent release of FSH and LH. An important note: inhibiting GnRH release inhibits FSH and LH release and thereby inhibits the ovarian cycle.

Ovaries

Uterus

Milk Ejection