Gonadal steroid hormone regulation of proopiomelanocortin gene expression in arcuate neurons that innervate the medial preoptic area of the rat

S. Cheung, Ronald P Hammer

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51 Citations (Scopus)

Abstract

The density of β-endorphin (β-endo)-like immunoreactive (IR) fibers in the medial preoptic area (MPOA) has been shown to vary across the estrous cycle and is gonadal steroid hormonedependent. These β-endo-containing fibers are presumably projections of proopiomelanocortin (POMC) neurons which are located in the arcuate nucleus (ARC). POMC mRNA level varies across the estrous cycle in the ARC and its expression is differentially altered by gonadal steroid hormones. However, it is unclear how gonadal steroids regulate POMC gene expression in ARC neurons that innervate the MPOA. Therefore, combined fluorogold (FG)) retrograde neuronal labeling and in situ hybridization histochemistry were used to investigate the effects of gonadal steroid hormone treatment on POMC gene expression in ARC neurons supplying the MPOA of ovariectomized (OVX) female rats. POMC-expressing cells were located in the ARC and median eminence (ME), wherein such neurons were significantly larger than unlabeled cells that surround them. A relatively greater number of ARC POMC neurons were observed to innervate the medial portion of the medial preoptic nucleus (MPN) than the lateral portion of the MPN. Estradiol (E2) and progesterone (P) treatment before FG injection did not affect the number of FG and POMC double-labeled neurons in the ARC, which suggests that hormone treatment did not alter the number of POMC-expressing neurons projecting to the MPN. In OVX animals, ARC POMC mRNA labeling was relatively low, and increased significantly in neurons of the most rostral ARC region 48 h after E2 treatment. P administration enhanced and prolonged the effect of E2 in this group of ARC neurons. E2P treatment significantly increased POMC mRNA expression beginning 13 h after P injection in all but the most caudal ARC POMC neurons. Thereafter, E2P treatment gradually increased POMC mRNA expression for at least 1 additional day. Gonadal steroid hormone treatment apparently affects POMC mRNA expression uniformly in neurons of the same ARC subdivision without regard to their efferent targets. Diurnal variation of POMC mRNA expression is present only in the most rostral ARC region, which contains a population of E2-sensitive POMC neurons. The results suggest that the relatively greater β-endo-like IR fiber density in the medial MPN is due to a greater number of POMC neurons innervating this region. The pattern of innervation of the MPN by POMC neurons is unaffected by gonadal steroid hormone treatment, which appears to induce POMC expression in ARC neurons, and eventually to stimulate the synthesis and transport of β-endo in POMC neuronal axons which project to the MPOA. That steroid hormones functionally influence ARC POMC mRNA expression suggests that ARC POMC neurons which innervate the MPN might play a role in control of reproductive behaviors that vary with hormone levels across the estrous cycle.

Original languageEnglish (US)
Pages (from-to)283-292
Number of pages10
JournalNeuroendocrinology
Volume62
Issue number3
StatePublished - 1995
Externally publishedYes

Fingerprint

Pro-Opiomelanocortin
Preoptic Area
Gene Expression Regulation
Gonadal Steroid Hormones
Arcuate Nucleus of Hypothalamus
Neurons
Messenger RNA
Estrous Cycle
Steroids
Hormones
Therapeutics
Endorphins

Keywords

  • Arcuate nucleus
  • Gonadal steroids
  • Opiate peptides
  • Preoptic area
  • Proopiomelanocortin

ASJC Scopus subject areas

  • Endocrinology
  • Neuroscience(all)

Cite this

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title = "Gonadal steroid hormone regulation of proopiomelanocortin gene expression in arcuate neurons that innervate the medial preoptic area of the rat",
abstract = "The density of β-endorphin (β-endo)-like immunoreactive (IR) fibers in the medial preoptic area (MPOA) has been shown to vary across the estrous cycle and is gonadal steroid hormonedependent. These β-endo-containing fibers are presumably projections of proopiomelanocortin (POMC) neurons which are located in the arcuate nucleus (ARC). POMC mRNA level varies across the estrous cycle in the ARC and its expression is differentially altered by gonadal steroid hormones. However, it is unclear how gonadal steroids regulate POMC gene expression in ARC neurons that innervate the MPOA. Therefore, combined fluorogold (FG)) retrograde neuronal labeling and in situ hybridization histochemistry were used to investigate the effects of gonadal steroid hormone treatment on POMC gene expression in ARC neurons supplying the MPOA of ovariectomized (OVX) female rats. POMC-expressing cells were located in the ARC and median eminence (ME), wherein such neurons were significantly larger than unlabeled cells that surround them. A relatively greater number of ARC POMC neurons were observed to innervate the medial portion of the medial preoptic nucleus (MPN) than the lateral portion of the MPN. Estradiol (E2) and progesterone (P) treatment before FG injection did not affect the number of FG and POMC double-labeled neurons in the ARC, which suggests that hormone treatment did not alter the number of POMC-expressing neurons projecting to the MPN. In OVX animals, ARC POMC mRNA labeling was relatively low, and increased significantly in neurons of the most rostral ARC region 48 h after E2 treatment. P administration enhanced and prolonged the effect of E2 in this group of ARC neurons. E2P treatment significantly increased POMC mRNA expression beginning 13 h after P injection in all but the most caudal ARC POMC neurons. Thereafter, E2P treatment gradually increased POMC mRNA expression for at least 1 additional day. Gonadal steroid hormone treatment apparently affects POMC mRNA expression uniformly in neurons of the same ARC subdivision without regard to their efferent targets. Diurnal variation of POMC mRNA expression is present only in the most rostral ARC region, which contains a population of E2-sensitive POMC neurons. The results suggest that the relatively greater β-endo-like IR fiber density in the medial MPN is due to a greater number of POMC neurons innervating this region. The pattern of innervation of the MPN by POMC neurons is unaffected by gonadal steroid hormone treatment, which appears to induce POMC expression in ARC neurons, and eventually to stimulate the synthesis and transport of β-endo in POMC neuronal axons which project to the MPOA. That steroid hormones functionally influence ARC POMC mRNA expression suggests that ARC POMC neurons which innervate the MPN might play a role in control of reproductive behaviors that vary with hormone levels across the estrous cycle.",
keywords = "Arcuate nucleus, Gonadal steroids, Opiate peptides, Preoptic area, Proopiomelanocortin",
author = "S. Cheung and Hammer, {Ronald P}",
year = "1995",
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volume = "62",
pages = "283--292",
journal = "Neuroendocrinology",
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T1 - Gonadal steroid hormone regulation of proopiomelanocortin gene expression in arcuate neurons that innervate the medial preoptic area of the rat

AU - Cheung, S.

AU - Hammer, Ronald P

PY - 1995

Y1 - 1995

N2 - The density of β-endorphin (β-endo)-like immunoreactive (IR) fibers in the medial preoptic area (MPOA) has been shown to vary across the estrous cycle and is gonadal steroid hormonedependent. These β-endo-containing fibers are presumably projections of proopiomelanocortin (POMC) neurons which are located in the arcuate nucleus (ARC). POMC mRNA level varies across the estrous cycle in the ARC and its expression is differentially altered by gonadal steroid hormones. However, it is unclear how gonadal steroids regulate POMC gene expression in ARC neurons that innervate the MPOA. Therefore, combined fluorogold (FG)) retrograde neuronal labeling and in situ hybridization histochemistry were used to investigate the effects of gonadal steroid hormone treatment on POMC gene expression in ARC neurons supplying the MPOA of ovariectomized (OVX) female rats. POMC-expressing cells were located in the ARC and median eminence (ME), wherein such neurons were significantly larger than unlabeled cells that surround them. A relatively greater number of ARC POMC neurons were observed to innervate the medial portion of the medial preoptic nucleus (MPN) than the lateral portion of the MPN. Estradiol (E2) and progesterone (P) treatment before FG injection did not affect the number of FG and POMC double-labeled neurons in the ARC, which suggests that hormone treatment did not alter the number of POMC-expressing neurons projecting to the MPN. In OVX animals, ARC POMC mRNA labeling was relatively low, and increased significantly in neurons of the most rostral ARC region 48 h after E2 treatment. P administration enhanced and prolonged the effect of E2 in this group of ARC neurons. E2P treatment significantly increased POMC mRNA expression beginning 13 h after P injection in all but the most caudal ARC POMC neurons. Thereafter, E2P treatment gradually increased POMC mRNA expression for at least 1 additional day. Gonadal steroid hormone treatment apparently affects POMC mRNA expression uniformly in neurons of the same ARC subdivision without regard to their efferent targets. Diurnal variation of POMC mRNA expression is present only in the most rostral ARC region, which contains a population of E2-sensitive POMC neurons. The results suggest that the relatively greater β-endo-like IR fiber density in the medial MPN is due to a greater number of POMC neurons innervating this region. The pattern of innervation of the MPN by POMC neurons is unaffected by gonadal steroid hormone treatment, which appears to induce POMC expression in ARC neurons, and eventually to stimulate the synthesis and transport of β-endo in POMC neuronal axons which project to the MPOA. That steroid hormones functionally influence ARC POMC mRNA expression suggests that ARC POMC neurons which innervate the MPN might play a role in control of reproductive behaviors that vary with hormone levels across the estrous cycle.

AB - The density of β-endorphin (β-endo)-like immunoreactive (IR) fibers in the medial preoptic area (MPOA) has been shown to vary across the estrous cycle and is gonadal steroid hormonedependent. These β-endo-containing fibers are presumably projections of proopiomelanocortin (POMC) neurons which are located in the arcuate nucleus (ARC). POMC mRNA level varies across the estrous cycle in the ARC and its expression is differentially altered by gonadal steroid hormones. However, it is unclear how gonadal steroids regulate POMC gene expression in ARC neurons that innervate the MPOA. Therefore, combined fluorogold (FG)) retrograde neuronal labeling and in situ hybridization histochemistry were used to investigate the effects of gonadal steroid hormone treatment on POMC gene expression in ARC neurons supplying the MPOA of ovariectomized (OVX) female rats. POMC-expressing cells were located in the ARC and median eminence (ME), wherein such neurons were significantly larger than unlabeled cells that surround them. A relatively greater number of ARC POMC neurons were observed to innervate the medial portion of the medial preoptic nucleus (MPN) than the lateral portion of the MPN. Estradiol (E2) and progesterone (P) treatment before FG injection did not affect the number of FG and POMC double-labeled neurons in the ARC, which suggests that hormone treatment did not alter the number of POMC-expressing neurons projecting to the MPN. In OVX animals, ARC POMC mRNA labeling was relatively low, and increased significantly in neurons of the most rostral ARC region 48 h after E2 treatment. P administration enhanced and prolonged the effect of E2 in this group of ARC neurons. E2P treatment significantly increased POMC mRNA expression beginning 13 h after P injection in all but the most caudal ARC POMC neurons. Thereafter, E2P treatment gradually increased POMC mRNA expression for at least 1 additional day. Gonadal steroid hormone treatment apparently affects POMC mRNA expression uniformly in neurons of the same ARC subdivision without regard to their efferent targets. Diurnal variation of POMC mRNA expression is present only in the most rostral ARC region, which contains a population of E2-sensitive POMC neurons. The results suggest that the relatively greater β-endo-like IR fiber density in the medial MPN is due to a greater number of POMC neurons innervating this region. The pattern of innervation of the MPN by POMC neurons is unaffected by gonadal steroid hormone treatment, which appears to induce POMC expression in ARC neurons, and eventually to stimulate the synthesis and transport of β-endo in POMC neuronal axons which project to the MPOA. That steroid hormones functionally influence ARC POMC mRNA expression suggests that ARC POMC neurons which innervate the MPN might play a role in control of reproductive behaviors that vary with hormone levels across the estrous cycle.

KW - Arcuate nucleus

KW - Gonadal steroids

KW - Opiate peptides

KW - Preoptic area

KW - Proopiomelanocortin

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