The Ovary Has Its Own Opioid Receptors That Change During the Menstrual Cycle | Research

The takeaway

Opioid receptors found on pig ovarian granulosa cells and corpora lutea increased during follicular maturation, directly linking opioids to ovarian function.

Cycle-dependent
Ovarian opioid receptor numbers increased during follicular maturation, suggesting dynamic opioid regulation of egg development

What the researchers found

Specific opioid receptors were found in pig granulosa cells and corpora lutea, with receptor numbers increasing during follicular maturation.

Why it matters

Finding opioid receptors directly in the ovary means opioid peptides can regulate fertility at the organ level, not just through the brain. This has implications for understanding how opioid drugs affect reproductive function.

How the study worked

Radioligand binding using [3H]naloxone in porcine granulosa cells and corpus luteum subcellular fractions. Competition binding with beta-endorphin, met-enkephalin, and dynorphin.

What this study cannot tell us

In vitro binding study in pig tissue. The functional significance of these receptors and their relevance to human ovarian biology need further study.

How to read the evidence

Preliminary — in vitro binding study in pig ovarian tissue. Functional significance not determined.

When this study was published

Published in 1995 (31 years ago). Ovarian opioid receptors have since been confirmed in multiple species.

The bigger picture

Finding opioid receptors directly on the ovary adds a new level to understanding opioid effects on fertility. Opioid drugs could affect egg maturation directly, not just through hormonal changes.

Questions still open

Do opioid drugs directly impair egg quality through these ovarian receptors?
Could ovarian opioid receptors be targeted for fertility treatment?

Common questions

Can opioid drugs directly affect the ovaries?

This study suggests yes — opioid receptors are present directly on ovarian cells, and their numbers change during the cycle. This means opioid drugs could affect egg maturation at the ovarian level, independent of brain hormonal effects.

Why do opioid receptors increase during egg maturation?

It suggests opioid signaling plays a role in the ovulation process. The increasing receptor numbers during maturation may help fine-tune the timing and quality of egg release.

Read the original research

[3H]naloxone binding sites in porcine ovarian follicles and corpora lutea during the ovarian cycle.

European journal of endocrinology, 132(5), 622-6

View on PubMed ↗

Citation

Hamada, H; Kishioka, S; Yamoto, M; Nakano, R. (1995). [3H]naloxone binding sites in porcine ovarian follicles and corpora lutea during the ovarian cycle.. European journal of endocrinology, 132(5), 622-6.