A "critical period" for cervically-stimulated prolactin relase

Area of Science:

• Reproductive Endocrinology
• Neuroendocrinology

Background:

• Pseudopregnancy in rats involves characteristic prolactin surges.
• The role of ovarian steroids in initiating and maintaining these surges is not fully understood.

Purpose of the Study:

• To investigate the necessity of ovarian steroids for prolactin surges induced by cervical stimulation.
• To determine if adrenal steroids influence these prolactin surges.
• To identify the timing dependency of cervically-induced prolactin release.

Main Methods:

• Ovariectomized rats underwent cervical stimulation to measure plasma prolactin.
• Experiments were repeated in adrenalectomized-ovariectomized rats.
• Cervical stimulation was performed at different times of day.

Main Results:

• Cervical stimulation in ovariectomized rats induced prolactin surges similar to intact pseudopregnant rats.
• Prolactin surges occurred even after removing ovaries and adrenal glands.
• Prolactin surges consistently peaked between 0300-0700 h, regardless of stimulation time, indicating a critical period.

Conclusions:

• Ovarian and adrenal steroids are not essential for the initiation or maintenance of prolactin surges post-cervical stimulation.
• Prolactin release is governed by a time-of-day "critical period" rather than the precise timing of the stimulus.