Further evidence for a significant participation of the melanocortin 4 receptor in the preovulatory prolactin surge in the rat.
We previously reported that the melanocortin 4 receptor may play a significant role in mediating the preovulatory surges of luteinizing hormone and prolactin in the rat. In order to confirm this previous finding, in the present study we examined and compared the effects of intracerebroventricular administrations of 1.0 nmol of MT II (a non-selective melanocortin 3 and 4 receptor agonist) and 10 nmol of gamma(1)-melanocyte-stimulating hormone (a selective melanocortin 3 receptor agonist) on luteinizing hormone and prolactin surges in starved, gonadal steroid-primed ovariectomized female rats, which is a model deprived of inherent surges of the two hormones. MT II significantly recovered the surge of prolactin, but not of luteinizing hormone (although a tendency to increase was seen), and gamma(1)-melanocyte-stimulating hormone was without effect on both hormones. This study corroborated our previous report through a different and direct approach that the melanocortin 4 receptor, but not the melanocortin 3 receptor, plays a significant role in mediating the preovulatory prolactin surge in the rat.
Watanobe
H
H
Third Department of Internal Medicine, Hirosaki University School of Medicine, Aomori, Japan. watah@iuhw.ac.jp
Yoneda
M
M
Kakizaki
Y
Y
Kohsaka
A
A
Suda
T
T
Schiöth
H B
HB
D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology; D005260:Female; D005508:Food Deprivation / Q000502:physiology; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood*; D010060:Ovulation / Q000187:drug effects / Q000502:physiology*; D011388:Prolactin / Q000097:blood*; D051381:Rats; D017208:Rats, Wistar; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin / Q000819:agonists / Q000378:metabolism*; D013997:Time Factors; D000521:alpha-MSH / Q000031:analogs & derivatives / Q000494:pharmacology; D019825:gamma-MSH / Q000494:pharmacology
D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin; C081720:alpha-MSH (4-10)amide, Ac-Nle(4)-cyclo(Asp(5)-Phe(7)-Lys(10))-; D019825:gamma-MSH; D000521:alpha-MSH; D011388:Prolactin; D007986:Luteinizing Hormone