Sexual dimorphism and sex steroid modulation of glial fibrillary acidic protein messenger RNA and immunoreactivity levels in the rat hypothalamus

Chowen, Julie A.; Busiguina, S.; García‐Segura, Luis M.

doi:10.1016/0306-4522(95)00250-m

Cited by 59 publications

(41 citation statements)

References 70 publications

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“…Not only does the number of glial processes change in response to sex steroids, but also the expression of glial acidic fibrillary protein (GFAP), a specific glial marker and structural protein. Male rats have higher levels of GFAP in the arcuate nucleus and neonatal castration results in levels similar to that seen in females (21). Both neonatal and adult testosterone treatment of neonatal castrated males and normal females results in GFAP levels similar to that found in normal males (21).…”

Section: Introductionmentioning

confidence: 59%

“…Male rats have higher levels of GFAP in the arcuate nucleus and neonatal castration results in levels similar to that seen in females (21). Both neonatal and adult testosterone treatment of neonatal castrated males and normal females results in GFAP levels similar to that found in normal males (21). Hence, sex steroid effects on synaptic remodelling are mediated, at least in part, through actions on astroglia.…”

Section: Introductionmentioning

confidence: 77%

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The regulation of GH secretion by sex steroids

Chowen

Frago

Argente

2004

European Journal of Endocrinology

106

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Gonadal sex steroids modulate GH synthesis and secretion with effects on both the hypothalamus and anterior pituitary. In the post-pubertal animal, androgens and oestrogens modulate hypothalamic somatostatin (SS) and GHRH synthesis respectively. These effects may be direct as SS neurons express the androgen receptor and many GHRH neurons are oestrogen receptor positive. The neonatal steroid environment modulates the number of GHRH neurons in the adult hypothalamus, as well as their responsivity to post-pubertal steroids. Furthermore, both neonatal and post-pubertal steroids modulate hypothalamic synaptic organisation affecting the number of synaptic inputs and the morphology of glial cells. This in turn has important effects on the ability of the hypothalamus to drive the secretory pulsatility of anterior pituitary hormone release. At the level of the somatotroph, androgens and oestrogens have been reported to stimulate, inhibit or have no effect on GH synthesis. In primary cultures, we found no effect of either androgens or oestrogens on GH mRNA levels. However, the sex steroid environment significantly modified the response of somatotrophs to SS. Furthermore, males have more somatotrophs compared with female rats and this partially depends on the neonatal sex steroid environment. In conclusion, sex steroids have both organisational and activational effects on the GH axis. These effects range from modulating the number of hypothalamic neurons controlling GH secretion, their responsiveness to later steroids, and the synaptic connectivity and neuropeptide production, to modulation of somatotroph numbers in the anterior pituitary and their responsiveness to inputs controlling GH synthesis and secretion.European Journal of Endocrinology 151 U95-U100

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Section: Introductionmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 77%

The regulation of GH secretion by sex steroids

Chowen

Frago

Argente

2004

European Journal of Endocrinology

106

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“…Consistent with this possibility is the observation that the glial fibrillary acidic protein-immunoreactivity of the astrocytic processes of the ARN is greater in male than in female rats (Chowen et al, 1995). Because there are studies showing that there are no sex-related differences in the numerical density of ARN astrocytes, evaluated by means of the optical disector (Chowen et al, 1995), it is likely, therefore, to assume that the ARN of males might contain a number of astrocytes higher than that of females given that the volume of the ARN is greater in male than in female rats.…”

Section: Sexual Dimorphism In the Arcuate Nucleusmentioning

confidence: 65%

Arcuate nucleus of the hypothalamus: Effects of age and sex

Leal¹,

Andrade²,

Paula‐Barbosa³

et al. 1998

J. Comp. Neurol.

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The arcuate nucleus of the hypothalamus (ARN) is involved in a variety of functions known to be sexually dimorphic and altered by aging. Although the effects of sex and age on the synaptic organization and neurochemistry of the ARN have been extensively analyzed, data regarding sex-related differences and age-induced effects on the total number of neurons and volume of the ARN in adult and aged male and female rats are controversial. To address this issue, we have quantitatively analyzed the ARN of male and female Wistar rats aged 6 and 24 months. The optical fractionator, the optical rotator, and the Principle of Cavalieri were used as the estimators of the total number of neurons, mean nuclear volume of ARN neurons, and volume of the ARN, respectively. In addition, a Golgi study was carried out to analyze the dendritic trees of its neurons. We found that in young adult rats, the volume of the ARN is 0.9 mm3 in males and 0.7 mm3 in females, whereas the total number of neurons is 100 x 10(3) in males and 86 x 10(3) in females. ARN neurons of males and females have identical mean nuclear volumes, which we estimated to be 300 microm3. No significant effects of age were found in these parameters, both in males and in females. In adult rats, no sex-related differences were detected in the number of dendritic segments and in the total dendritic length, but the dendritic branching density and the spine density were greater in females than in males. In aged rats there was a significant reduction in the number of dendritic segments, in the total dendritic length, and in the branching and spine densities that, although evident in both sexes, was more marked in females. Our results show that the total number of neurons and the volume of the ARN are sexually dimorphic in adult and aged rats and that neither of these parameters is altered by aging. Conversely, aging induces regressive changes in the dendritic arborizations of ARN neurons of males and females and abolishes the sexual dimorphic pattern of their organization.

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“…Indeed, organizational effects of testosterone on astroglia [6] parallel effects of this hormone on the num ber of GHRH neurones in the rat arcuate nucleus [7], while activational effects of testosterone on astroglia [6] parallel effects of this hormone on GHRH expression [7], Figure 1 is a summary of these studies. Immunoreactivity of GFAP, GFAP mRNA levels, GHRH mRNA levels, and the number of GHRH-expressing cells were all de creased by the neonatal castration of males.…”

Section: Gonadal Hormone Regulation Of Astroglia and Hypothalamic Hormentioning

confidence: 95%

“…GHRH mRNA signal levels, GFAP mRNA signal levels, and GFAP immunoreactivity in the arcuate nucleus of the hypothalamus of adult rats. Signal levels of mRNA were measured by in situ hybridization and are expressed as autoradiographic grains per cell or densitometric units [6,7], GFAP immunoreactivity was measured by immunohistochemistry and is expressed as the surface density of immunoreactive cells [7], The experimental groups for male animals are as follows: IM. the number of GHRH-expressing cells and the levels of GFAP, while the administration of testosterone to adult females increased the expression of both GHRH and GFAP.…”

Section: Gonadal Hormone Regulation Of Astroglia and Hypothalamic Hormentioning

confidence: 99%

The Role of Glia in the Neuroendocrine Hypothalamus: Possible Implications in Hormone Secretion

Chowen

Argente²,

Busiguina³

et al. 1996

Horm Res

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Recent evidence indicates that glia may play a significant role in the link between the endocrine and nervous systems. Gonadal steroids modulate astroglia morphology, differentiation and gene expression in different brain areas. Hormonal effects on glia may have important consequences for neuronal development, metabolism and activity, for the formation and plasticity of synaptic connections, and for the modulation of hypothalamic hormone release. Perinatal and adult testosterone levels modulate the expression of the specific astroglia cytoskeletal marker glial fibrillary acidic protein in the arcuate nucleus of the rat hypothalamus. These changes parallel hormonal effects on the expression of growth hormone-releasing hormone (GHRH) and the number of GHRH neurones in the arcuate nucleus. The effects of testosterone and its metabolite oestradiol on hypothalamic neurones may be dependent on the release by hypothalamic astroglia of insulin-like growth factor I, a molecule involved in the control of growth hormone secretion.

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Sexual dimorphism and sex steroid modulation of glial fibrillary acidic protein messenger RNA and immunoreactivity levels in the rat hypothalamus

Cited by 59 publications

References 70 publications

The regulation of GH secretion by sex steroids

The regulation of GH secretion by sex steroids

Arcuate nucleus of the hypothalamus: Effects of age and sex

The Role of Glia in the Neuroendocrine Hypothalamus: Possible Implications in Hormone Secretion

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