Immunocytochemical Localization of Insulin-Like Growth Factor I in the Hypothalamo-Hypophyseal System of the Adult Rat

Aguado, Fernando; Fernandez, Teresa de Souza; Martı́nez-Murillo, Ricardo; Rodrigo, José; Cacicedo, Lucinda; Sánchez‐Franco, Franco

doi:10.1159/000126317

Cited by 19 publications

(12 citation statements)

References 31 publications

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“…Previous immunocytochemical studies have shown that arcuate neurons in young rats are highly immunore active for IGF-I [22], Furthermore, by using polyclonal antibodies for IGF-I, we and others have found that IGF-I-like immunoreactivity remains detectable in some ar cuate neurons in adult rats while decreasing in other brain areas [ 16,22], Our present findings, based on the use of a monoclonal antibody, show that the surface density of IGF-I-like immunoreactive glial profiles increases in the arcuate nucleus of both male and female rats at the time of puberty. This change contrasts with the overall decrease in IGF-I immunoreactivity in glial cells observed with age in other brain regions [22,23].…”

Section: Discussionsupporting

confidence: 51%

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Gonadal Hormone Regulation of Insulin-Like Growth Factor-I Like Immunoreactivity in Hypothalamic Astroglia of Developing and Adult Rats

et al. 1994

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The influence of gonadal steroids on insulin-like growth factor I (IGF-I)-like immunoreactivity was assessed in the rat arcuate nucleus, an area of the hypothalamus that regulates pituitary secretion. IGF-I-like immunoreactivity was observed in hypothalamic cells with the morphological aspects of tanycytes and astrocytes. The surface density of IGF-I-like immunoreactive glia increased with puberty in the arcuate nucleus of male and female rats, while decreasing with age in other brain areas. Gender differences in the surface density of IGF-I-like immunoreactive glia were detected in adult animals, with males and androgenized females having significantly higher values than normal females. In the latter, the surface density of IGF-I-like immunoreactive glia was increased in the afternoon of proestrus and in the morning of estrus compared to the morning of proestrus, diestrus and metestrus. In addition, IGF-I-like immunoreactivity showed a dose-dependent increase in ovariectomized rats injected with 17β-estradiol, but not in those receiving 17α-estradiol. The effect of 17β-estradiol was blocked by simultaneous administration of progesterone, while this hormone alone had no effect. These results indicate that IGF-I-like immunoreactivity in arcuate glial cells is affected by the hormonal environment and suggest that IGF-I-like immunoreactive glia may be involved in neuroendocrine events within the hypothalamus.

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Section: Discussionsupporting

confidence: 51%

“…Both antisera have been characterized in previous studies [15][16][17], Dot blot analysis revealed that the polyclonal antiserum has a 30% higher affinity for the truncated IGF-I form, (4-70)lGF-I. present in brain tissue [18] compared to the affinity for the intact IGF-I form present in plasma.…”

Section: Immunohistochemislrymentioning

confidence: 99%

Gonadal Hormone Regulation of Insulin-Like Growth Factor-I Like Immunoreactivity in Hypothalamic Astroglia of Developing and Adult Rats

et al. 1994

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“…IGF-I antiserum raised in rabbits in our laboratory was validated and tested in previous studies [5, 8]. Briefly, human recombinant IGF-I (1–70; Bachem, Torrance, Calif., USA) was coupled with carbodiimide [12]to bovine serum albumin (Sigma Chemical Co., St Louis, Mo., USA) to form the conjugate that was used as immunogen.…”

Section: Methodsmentioning

confidence: 99%

“…It has been shown [4]that IGF-I of peripheral origin contributes to the initiation of female puberty by stimulating GnRH release from the hypothalamus. We and others have reported that IGF-I and its receptor are expressed in the hypothalamus and median eminence (ME) [5, 6, 7]. Therefore, centrally located IGF-I may regulate GnRH through autocrine, paracrine or endocrine functions within the hypothalamus.…”

Section: Introductionmentioning

confidence: 99%

Regulation of Gonadal and Somatotropic Axis by Chronic Intraventricular Infusion of Insulin-Like Growth Factor 1 Antibody at the Initiation of Puberty in Male Rats

Pazos

Sánchez‐Franco²,

Balsa³

et al. 1999

Neuroendocrinology

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There has been increasing experimental evidence to suggest that insulin-like growth factor 1 (IGF-I) may be one of the essential regulators in the reproductive system of the rat. IGF-I is synthesized in the hypothalamus and IGF-I immunoreactivity increases during puberty. Consequently we hypothesized that centrally located IGF-I might contribute to the initiation of puberty. Centrally located IGF-I was immunoneutralized to assess this hypothesis. Male Wistar rats, 28 days old, were infused intracerebroventricularly with specific purified IgGs from rabbit IGF-I antiserum (IGF-I-Ab). The intracerebroventricular administration of IGF-I-Ab resulted in a reduction in testicular weight and consequently in delayed pubertal development. There was also a reduction in serum testosterone, pituitary immunoreactive (IR) luteinizing hormone (LH) and serum IR follicle-stimulating hormone (FSH). The accumulation of βLH mRNA was not modified, whereas βFSH mRNA was increased. An increment in the serum growth hormone (GH) levels was also observed. There were no significant alterations in hypothalamic IR growth hormone releasing factor content, although IR somatostatin (SRIH) content was increased by IGF-I-Ab. The body weight gain remained unaltered. As a whole, our study suggests that centrally located IGF-I influences pubertal development, production and release of gonadotropins and supports the finding that endogenous centrally located IGF-I plays a role at the initiation of puberty in the male rat. It also gives support to the physiological role of centrally located IGF-I in the release of GH mediated by hypothalamic SRIH at the initiation of puberty.

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“…These two mechanisms act in concert to finely modulate neuronal activity Voisin and Bourque, 2002). IGF-1 immunoreactivity and mRNA have been observed in adult SON neurons (Aguado et al, 1992;Zhou et al, 1999), and high expression of the IGF-1 receptor has been reported in the SON (Folli et al, 1994;Cardona-Gomez et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Insulin-Like Growth Factor-1 Inhibits Adult Supraoptic Neurons via Complementary Modulation of Mechanoreceptors and Glycine Receptors

Ster¹,

Colomer²,

Monzo³

et al. 2005

J. Neurosci.

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In the CNS, insulin-like growth factor-1 (IGF-1) is mainly known for its trophic effect both during development and in adulthood. Here, we show than in adult rat supraoptic nucleus (SON), IGF-1 receptor immunoreactivity is present in neurons, whereas IGF-1 immunoreactivity is found principally in astrocytes and more moderately in neurons. In vivo application of IGF-1 within the SON acutely inhibits the activity of both vasopressin and oxytocin neurons, the two populations of SON neuroendocrine cells. Recordings of acutely isolated SON neurons showed that this inhibition occurs through two rapid and reversible mechanisms, both involving the neuronal IGF-1 receptor but different intracellular messengers. IGF-1 inhibits Gd 3ϩ -sensitive and osmosensitive mechanoreceptor cation current via phosphatidylinositol-3 (PI3) kinase activation. IGF-1 also potentiates taurine-activated glycine receptor (GlyR) Cl Ϫ currents by increasing the agonist sensitivity through a extremely rapid (within a second) PI3 kinase-independent mechanism. Both mechanoreceptor channels and GlyR, which form the excitatory and inhibitory components of SON neuron osmosensitivity, are active at rest, and their respective inhibition and potentiation will both be inhibitory, leading to strong decrease in neuronal activity. It will be of interest to determine whether IGF-1 is released by neurons, thus participating in an inhibitory autocontrol, or astrocytes, then joining the growing family of glia-to-neuron transmitters that modulate neuronal and synaptic activity. Through the opposite and complementary acute regulation of mechanoreceptors and GlyR, IGF-1 appears as a new important neuromodulator in the adult CNS, participating in the complex integration of neural messages that regulates the level of neuronal excitability.

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Immunocytochemical Localization of Insulin-Like Growth Factor I in the Hypothalamo-Hypophyseal System of the Adult Rat

Cited by 19 publications

References 31 publications

Gonadal Hormone Regulation of Insulin-Like Growth Factor-I Like Immunoreactivity in Hypothalamic Astroglia of Developing and Adult Rats

Gonadal Hormone Regulation of Insulin-Like Growth Factor-I Like Immunoreactivity in Hypothalamic Astroglia of Developing and Adult Rats

Regulation of Gonadal and Somatotropic Axis by Chronic Intraventricular Infusion of Insulin-Like Growth Factor 1 Antibody at the Initiation of Puberty in Male Rats

Insulin-Like Growth Factor-1 Inhibits Adult Supraoptic Neurons via Complementary Modulation of Mechanoreceptors and Glycine Receptors

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