The Role of Oxytocin as a Neurotransmitter in Breastfeeding - An Overview

Introduction

Oxytocin is a neurohormone that plays a vital role in integrating several physiological functions between lactating mothers and babies during breastfeeding. The pathways of oxytocin functioning are unique and diverse. While its role as a hormone is widely known and documented, its action as a neurotransmitter is less frequently studied. Oxytocin also exhibits neuronal activities influencing behavior such as bonding and caring which is essential for successful breastfeeding and childcare. Its dual action is attributed to the simultaneous release of oxytocin into the circulating blood as well as the central nervous system. oxytocin functions as a potent hormone and also as a neurotransmitter by producing diverse responses, especially in the brain.

Is Oxytocin a Hormone or Neurotransmitter?

Neurotransmitters are commonly known as chemical transmitters or chemical messengers. They belong to a group of endogenous (produced within the body) chemicals that are present at the endings of nerve cells (neurons) and are released to stimulate the target neurons, muscles, or gland cells. Thus, the generated impulses are passed from one cell to another and spread throughout the nervous system. These neurotransmitters are synthesized by nerve cells and are stored in pouch-like vesicles (present in the neuron’s terminal end). On receiving activating signals, they are released to carry out their biological function.

Hormones, on the other hand, are organic substances that are directly secreted into the blood circulation from their synthesis site on receiving stimulating signals from the pituitary (master gland) through stimulating hormones. Through blood, hormones reach their target site to carry out physiological activities. In both males and females, oxytocin is synthesized and stored in the hypothalamus (a part of the brain). It is secreted into the main bloodstream through the posterior (back in position) pituitary gland. Smaller amounts of oxytocin are also synthesized and secreted by other tissues such as the brain, uterus, ovaries, testes, and placenta.

• As a hormone - oxytocin is essential to regulate reproductive functions.

• It acts on muscle cells and causes contractions in the uterus (during childbirth) and mammary glands (during lactation).

• As a neurotransmitter - the neurotransmitter functions of oxytocin involve modulating neuroendocrine reflexes such as the milk-ejection reflex, establishing highly evolved social and bonding behaviors, which are commonly associated with reproduction and offspring caring.

• Oxytocin ensures the physiological, behavioral, and neuroendocrinal changes specific to lactation that are effectively regulated in and around the time of delivery and breastfeeding (peripartum period).

What Is the Role of Oxytocin as a Neurotransmitter in Lactating Mothers?

During breastfeeding, oxytocin is released from the brain (hypothalamus) of the mother and induces various functional and biological responses. The following are the effects of oxytocin as a neurotransmitter in breastfeeding mothers.

• The release of oxytocin during lactation occurs through neuronal stimulation. During the suckling of the breastfeeding mother’s nipples by infants, the sensory nerves present in the breast send stimulating sensory impulses.

• It is also stimulated by skin-to-skin contact between the mothers and the infants where the sensory nerves are stimulated due to warmth, touch, light pressure, and gentle strokes.

• Oxytocin is essential for milk removal and milk ejection (letdown reflex). Following suckling, the myoepithelial (muscle) cells present in the breasts contract under the influence of oxytocin and push the formed milk from the milk-storing cells (alveoli) through the milk ducts toward the nipples.

• Oxytocin release is pulsatile (periodic rhythm) and the pulses are generated at 90-second intervals during the first 10 minutes of breastfeeding and in the initial few days after childbirth.

• Oxytocin-induced effects on the brain of breastfeeding mothers result in positive outcomes involving lactation and mother-baby interactions.

• In breastfeeding mothers, oxytocin causes physiological and psychological adaptations such as greater social interactions and effectively reduces anxiety.

• It decreases cortisol levels and lowers blood pressure.

• It regulates the proper functioning of the gastrointestinal tract.

• These effects of circulating oxytocin levels are predominantly neuronal and are reflected in the brain which proves the fact that oxytocin is a neurotransmitter that is parallelly released into the systemic circulation and also into the brain.

What Is the Role of Oxytocin as a Neurotransmitter in Infants?

Oxytocin is produced in infants as it is initiated during fetal life and increased during breastfeeding. Recent studies have been undertaken to understand the infant-oxytocin system and its biological impact. The effects of oxytocin as a neurotransmitter in infants are as follows -

• Oxytocin levels are greater in infants when compared to mothers and are influenced by the mode of childbirth.

• Oxytocin levels are elevated in the umbilical arterial blood of babies through vaginal delivery when compared with babies born by c-section (cesarean section).

• These differences subside in subsequent days; however, infants continue to maintain increased oxytocin levels than their mothers.

• These oxytocin levels are associated with developing good feelings and positive emotions in babies which helps them to build trust with their parents or caregivers.

• The infant-oxytocin release is primarily triggered by suckling in newborns during breastfeeding.

• This effect is due to the activation of sensory nerves present in the baby's oral mucosa that occurs during active milk removal when breastfed.

• Light pressure, warmth, caring touch, and stroking experienced by the babies during breastfeeding result in pleasant non-noxious sensory skin stimulation that contributes to oxytocin release.

• This neuronal activation of oxytocin improves breastfeeding interactions between mother and infant by facilitating interactive social behaviors and synchronizing their mutual interactions.

• Oxytocin induces calmness in both mother and infant which is noticed by the infant crying less, and the ability to bear the pain (pain threshold increased).

• Stress hormones, such as cortisol levels are decreased and the skin temperature around the mother’s breast and that of the infant increases.

What Is the Impact of Oxytocin as a Neurotransmitter in Breastfeeding?

The act of suckling during breastfeeding enhances bonding between the mothers and the babies due to the action of oxytocin as a neurotransmitter since these signals are transmitted by neural stimulation. Its impact on breastfeeding is as follows -

• Oxytocin influences infants’ attachment to their mothers and helps in creating primitive attachment behavior in newborns and babies.

• Neuronal stimulation increases milk flow in mothers during breastfeeding by enhancing the letdown reflex which causes an adequate supply of milk to the babies.

• It also increases the width of the milk ducts by nerve stimulation which prevents the clogging of ducts and ensures the free flow of milk.

• Research studies show that mothers who have breastfed for a longer duration have lower to normal systolic, and diastolic blood pressure and experience reduced stress reactivity.

• The anti-stress effects of oxytocin are attributed to its neurotransmitter role as it inhibits the release of stress hormones (adrenaline) by the negative feedback mechanism.

• The neural activity of oxytocin is well-regulated in infants experiencing closeness and friendly behaviors from parents and primary caregivers.

• This ensures a sustained state of satisfaction and develops calmness leading to secure attachment.

Conclusion:

Oxytocin as a neurotransmitter causes prolonged implications in both mother and baby wellness. It is not only essential for milk ejection from lactating mothers but is also needed for the infant’s behavioral development and is influenced by positive breastfeeding practices. Exploring the neuronal functions of oxytocin would help in inducing positive social and adaptive patterns not only in infants but also in their later stages of life.