Differential
Regulation of Preovulatory Luteinizing Hormone
and Follicle-Stimulating Hormone Release by
Opioids in the Proestrous Rat
S. KUMRU, M. ªIMªEK,
B. YILMAZ*, E. SAPMAZ, S. KUTLU*,
S. SANDAL*, S. CANPOLAT*
Firat
University Medical School, Departments of
Obstetrics and Gynecology, and *Physiology,
Elazig, Turkey
Received June 1, 2000
Accepted December 13, 2000
Summary
We
have investigated the role of m- and k-opioid
receptors in the central control of preovulatory
LH and FSH release in the proestrous rat. Animals
were anesthetized with chloral hydrate at 14:00 h
on proestrus day. Following femoral artery
cannulation, they were mounted in a stereotaxic
apparatus. Morphine and U-50488H
(benzene-acetamide methane sulphonate) were
infused intracerebroventricularly either alone or
in combination with naloxone and MR1452,
respectively. Controls received sterile saline
alone. Blood samples were obtained at hourly
intervals between 15:00 h and 17:00 h. Plasma LH
and FSH levels were measured by radioimmunoassay.
Morphine did not significantly change plasma LH
levels at 15:00 h and 16:00 h sampling intervals.
A significant increase was observed at 17:00 h
compared to the controls (p<0.05). U-50488H
significantly increased LH levels at 16:00 h and
17:00 h (p<0.05). The co-administration of
naloxone and MR1452 with m- and k-agonist had no
significant effect on LH levels at any sampling
interval. In all groups, LH levels showed a
linear rise over the sampling period between
15:00 h and 17:00 h. None of the treatments
significantly altered plasma FSH levels which
however, declined towards the end of the
afternoon surge. In conclusion, we suggest that
the secretion of LH and FSH is differentially
regulated by m- and k-opioid receptors. It is
thought that in all groups chloral hydrate
interfered with the LH surge secretory systems.
Key
words
LH
· FSH · Morphine · Naloxone · U-50488H ·
MR1452
Reprint
requests
Dr.
Bayram Yilmaz, Firat University, Tip Fakültesi
(Medical School), Department of Physiology, 23119
Elazig, Turkey. Fax: + 90 424 237 91 38. E-mail: b.yilmaz@excite.com
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