Effect of gonadal steroids upon hypothalamic oxytocin expression
J A Amico1, R S Crowley, T R Insel
1University of Pittsburgh School of Medicine, PA, USA.
Advances in Experimental Medicine and Biology
|January 1, 1995
Summary
Estrogen and progesterone withdrawal significantly increase oxytocin (OT) mRNA in the rat hypothalamus. This finding clarifies the role of gonadal steroids in regulating OT gene expression during reproductive events.
Area of Science:
- Neuroendocrinology
- Reproductive Biology
- Molecular Endocrinology
Background:
- Oxytocin (OT) plays a crucial role in reproductive functions.
- The precise influence of gonadal steroids on OT gene expression in vivo remains unclear.
- Estrogen (E) is known to induce OT expression in vitro, but in vivo evidence in the hypothalamus is limited.
Purpose of the Study:
- To investigate the in vivo effect of estrogen and progesterone on oxytocin mRNA levels in the rat hypothalamus.
- To elucidate the role of gonadal steroid withdrawal in regulating hypothalamic OT gene expression.
- To examine the coordinated expression of OT and vasopressin (AVP) mRNA during specific reproductive states.
Main Methods:
- Ovariectomized rats were treated with estrogen (E) and progesterone (P) implants, followed by P withdrawal.
- In situ hybridization and Northern blot analyses were used to quantify OT and AVP mRNA levels in the hypothalamus.
- Physiological states including late pregnancy and lactation were studied.
Main Results:
- Estrogen and progesterone withdrawal significantly increased oxytocin (OT) mRNA levels in the rat hypothalamus.
- No significant change in vasopressin (AVP) mRNA was observed.
- Similar OT mRNA induction was noted in late pregnancy and lactation, correlating with progesterone withdrawal or suckling interruption.
Conclusions:
- Progesterone withdrawal is pivotal in inducing hypothalamic OT gene expression in estrogen-primed rats.
- Estrogen and progesterone dynamics, particularly withdrawal, are critical regulators of oxytocin synthesis during reproduction.
- This study provides in vivo evidence for the regulation of hypothalamic oxytocin by gonadal steroids.
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