Suckling-induced serum prolactin levels are modified by interference with milk ejection in lactating rats

Area of Science:

• Reproductive Biology
• Endocrinology
• Lactation Physiology

Background:

• Prolactin (PRL) is crucial for lactation and is typically released in response to suckling stimuli.
• Milk ejection is a complex process involving hormonal and neural pathways, essential for efficient milk transfer.
• Disruptions in milk ejection can lead to mammary gland engorgement, potentially impacting hormonal feedback mechanisms.

Purpose of the Study:

• To investigate the relationship between impaired milk ejection and suckling-induced prolactin (PRL) levels.
• To determine the role of mammary gland engorgement in regulating PRL release during lactation.

Main Methods:

• Milk ejection was impaired in lactating dams using two models: maternal sleep deprivation and extended nonsuckling intervals.
• Serum PRL levels were measured in response to suckling stimuli under conditions of impaired milk ejection and varying degrees of mammary gland engorgement.
• Mammary gland weight was assessed as an indicator of engorgement.

Main Results:

• Sleep deprivation, which blocked milk ejection, enhanced suckling-induced PRL levels in dams separated from pups, leading to mammary gland engorgement.
• In sleep-deprived dams, PRL levels decreased when engorged mammary glands were artificially evacuated via oxytocin injection.
• Increased nonsuckling intervals impaired milk ejection and correlated with increased mammary gland weight and elevated suckling-induced PRL levels.

Conclusions:

• Mammary gland engorgement, rather than suckling stimuli alone, plays a significant role in regulating suckling-induced PRL levels when milk ejection is impaired.
• The findings suggest a feedback mechanism where mammary gland status influences the prolactin response to suckling.