The central effect of beta-endorphin and naloxone on the expression of GnRH Gene and GnRH receptor (GnRH-R) gene in the hypothalamus, and on GnRH-R gene in the anterior pituitary gland in follicular phase ewes.
The effect of prolonged intermittent infusion of beta-endorphin or naloxone into the third cerebral ventricle in ewes during the follicular phase of the estrous cycle on the expression of GnRH gene and GnRH-R gene in the hypothalamus and GnRH-R gene in the anterior pituitary gland was examined by Real time-PCR. Activation of micro opioid receptors decreased GnRH mRNA levels in the hypothalamus and led to complex changes in GnRH-R mRNA: an increase of GnRH-R mRNA in the preoptic area, no change in the anterior hypothalamus and decrease in the ventromedial hypothalamus and stalk/median eminence. In beta-endorphin treated ewes the levels of GnRH-R mRNA in the anterior pituitary gland also decreased significantly. These complex changes in the levels of GnRH mRNA and GnRH-R mRNA were reflected in the decrease of LH secretion. Blockade of micro opioid receptors affected neither GnRH mRNA and GnRH-R mRNA nor LH levels secretion. These results indicate that beta-endorphin displays a suppressive effect on the expression of the GnRH gene in the hypothalamus and GnRH-R gene in the anterior pituitary gland, but affects GnRH-R gene expression in a specific manner in the various parts of hypothalamus; altogether these events lead to the decrease in GnRH/LH secretion.
Ciechanowska
M O
MO
Department of Neuroendocrinology, The Kielanowski Institute of Animal Physiology and Nutrition Polish Academy of Science, Jablonna, Poland. m.ciechanowska@ifzz.pan.pl
Lapot
M
M
Malewski
T
T
Mateusiak
K
K
Misztal
T
T
Przekop
F
F
D000818:Animals; D001947:Breeding; D030762:Estrous Cycle; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics*; D007031:Hypothalamus / Q000737:chemistry / Q000187:drug effects*; D007986:Luteinizing Hormone / Q000378:metabolism; D009270:Naloxone / Q000008:administration & dosage*; D010903:Pituitary Gland, Anterior / Q000737:chemistry / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D011966:Receptors, LHRH / Q000235:genetics; D012621:Seasons; D012756:Sheep / Q000378:metabolism*; D001615:beta-Endorphin / Q000008:administration & dosage*
D012333:RNA, Messenger; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D009270:Naloxone; D001615:beta-Endorphin; D007986:Luteinizing Hormone