Hypothalamic Expression of Melanocortin-4 Receptor and Agouti-related Peptide mRNAs During the Estrous Cycle of Rats

Document Type : Original Article

Authors
Mohammad Reza Zandi 1
Mohammad Reza Jafarzadeh Shirazi 1
Amin Tamadon 2
Amir Akhlaghi 1
Mohammad Saied Salehi 1
Ali Niazi 3
Ali Moghadam
1 Department of Animal Sciences, School of Agriculture, Shiraz University, Shiraz, Iran
2 Transgenic Technology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
3 Biotechnology Research Center, School of Agriculture, Shiraz University, Shiraz, Iran
Abstract
Melanocortin- 4 receptor (MC4R) and agouti- related peptide (AgRP) are involved in energy homeostasis in rats.
According to MC4R and AgRP effects on luteinizing hormone (LH) secretion, they may influence the estrous
cycle of rats. Therefore, the aim of this study was to investigate the expression of MC4R and AgRP mRNAs at
different stages of estrous cycle in the rat’s hypothalamus. The estrous cycle stages (proestrus, estrus, metestrus
and diestrus) were determined in 20 adult female rats using vaginal smears. The rats were divided into four equal
groups (n=5). Four ovariectomized rats were selected as controls two weeks after surgery. Using real- time PCR,
relative expressions (compared to controls) of MC4R and AgRP mRNAs in the hypothalamus of rats were
compared in four different groups of estrous cycle. The relative expression of MC4R mRNA in the
hypothalamus of female rats during proestrus stage was higher than those in other stages (P=0.001). Despite a
lower mean of relative expression of AgRP mRNA at proestrus stage, the relative expression of AgRP mRNA of
the four stages of estrous cycle did not differ (P>0.05). In conclusion, changes in the relative expression of
MC4R and AgRP mRNAs in four stages of rat estrous cycle indicated a stimulatory role of MC4R in the
proestrus and preovulatory stages and an inhibitory role of AgRP in gonadotropin releasing hormone (GnRH)
and LH secretions.
Keywords
Melanocortin- 4 receptor
agouti- related peptide
hypothalamus
estrous cycle
rat