Substance P in the Median Eminence and Pituitary of the Rat: Demonstration of Immunoreactive Fibers and Specific Binding Sites

Mikkelsen, Jens D.; Larsen, Philip J.; Møller, Morten Hylander; Vilhardt, Hans; Særmark, T.

doi:10.1159/000125208

Cited by 64 publications

(22 citation statements)

References 16 publications

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“…1 A and B). Furthermore, we also observed SP-ir fibers and terminals in the AP and in the posterior pituitary (data not shown), which have been described in rat, monkey, and human (7)(8)(9)(10)(11)(12) Colocalization studies showed that most SP-ir cells within the male AP were double-labeled with GH antiserum (Fig. 1 D, E, and F).…”

Section: Resultssupporting

confidence: 71%

“…Furthermore, it is possible that OX increased the number of SP-ir thyrotrophs but that levels ofSP expression were below sensitivity ofthe immunogold staining technique. DISCUSSION SP is present in nerve fibers and cell bodies in the posterior pituitary and in the AP of several species (5)(6)(7)(8)(9)(10)(11)(12). Because SP may act directly at the level of the AP to induce PRL secretion (18,19,22,27) (12) that SP does not colocalize with GH, and in guinea pig (5) and human (12) AP SP immunoreactivity is detected in TSH cells.…”

Section: Resultsmentioning

confidence: 99%

“…Substance P (SP) immunoreactivity has been detected in the rat anterior pituitary (AP) by RIA (1)(2)(3)(4) and by immunohistochemistry in several species (5)(6)(7)(8)(9)(10)(11)(12), and SP may act as a local modulator of pituitary function. Northern (RNA) blot and nuclease-protection analyses of RNA isolated from rat APs have revealed the presence of SP-encoding mRNAs in the gland (4,13,14), indicating that cells within the AP synthesize SP.…”

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confidence: 99%

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Sexually dimorphic distribution of substance P in specific anterior pituitary cell populations.

Brown

Roth

Krause

1991

Proc. Natl. Acad. Sci. U.S.A.

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Substance P (SP) immunoreactivity is detectable in the rat pituitary by RIA; however, immunollization has been difficult. We used a sensitive immunogold silverenhancement staining technique to cytochemically locate SP in the gland. SP-lmmunoreactive (SP-ir) cells were seen in anterior pituitary (AP), and occasional SP-ir fibers and terminals were seen in both AP and posterior pituitary. Coloalization studies showed the vast majority of SP-ir cells in the male AP to be also immunoreactive for growth hormone (GH). These GH/SP-ir cells represent -23% ofthe somatotroph population in the male. SP-ir cells did not colocalize with lactotrophs, gonadotrophs, or corticotrophs; however, rare thyroidstimulating hormone/SP-ir cells were found in the male AP. Comparisons of pituitaries from males and females revealed that females have 70% fewer SP-Ir cells and that only =%6% of the somatotrophs in the female express SP. This sexual dimorphism is diminished in 6-day ovariectomized rats because this treatment increases the GH/SP-ir cell population 3-fold. This result suggests that the previously reported estrogen-induced decrease in SP gene and peptide expression in the pituitary occurs, at least in part, in a subpopulation of somatotrophs. To test this hypothesis, distribution of SP-ir cells was examined in pituitaries from estrogen-and oil-treated ovariectomized rats. Estrogen reduced the percentage of somatotrophs with SP immunoreactivity by 70% compared with ovariectomized oiltreated controls, indicating that estrogen most likely regulates SP levels in the pituitary by acting on a subpopulation of somatotrophs to suppress SP expression. Estrogen does not appear to alter SP immunoreactiviy that is detected in the additional population of SP cells that colocalize with thyroidstimulating hormone. These SP-expressing thyrotrophs were seen 6-fold more frequently in the female than in the male pituitary, regardless of steroid status. These studies reveal that males have more total SP-ir cells in the AP than do females and that there is a sexually dimorphic pattern of SP distribution in the gland. Males have a higher percentage of SP-ir GH cells, whereas females have more SP-ir thyrotrophs than do males. Identification of independently regulated SP-ir somatotroph and thyrotroph populations provides a basis for investigating the roles of SP in autocrine or paracrine regulation of pituitary hormone secretion.Substance P (SP) immunoreactivity has been detected in the rat anterior pituitary (AP) by RIA (1-4) and by immunohistochemistry in several species (5-12), and SP may act as a local modulator of pituitary function. Northern (RNA) blot and nuclease-protection analyses of RNA isolated from rat APs have revealed the presence of SP-encoding mRNAs in the gland (4, 13, 14), indicating that cells within the AP synthesize SP. Furthermore, SP content in the AP is regulated by gonadal steroids: androgens increase and estrogen decreases pituitary SP levels (2-4), resulting in a sexual dimorphism, such that males have a higher SP co...

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Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Sexually dimorphic distribution of substance P in specific anterior pituitary cell populations.

Brown

Roth

Krause

1991

Proc. Natl. Acad. Sci. U.S.A.

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“…The SP neurons are widely distributed in the hypothalamus [26] and also send SP fibers to the external layer of the median eminence [27, 28]. Moreover, earlier studies have shown the central effect of SP on gonadotropin release [12, 13, 14, 15, 16, 17].…”

Section: Discussionmentioning

confidence: 99%

Increase of Gonadotropin-Releasing Hormone Concentration in Pituitary Portal Blood after Substance P Administration in Male Rats

Walczewska¹,

Szkudlarek²,

Jakubowska-Naziemblo³

et al. 1998

Neuroendocrinology

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Substance P (SP) affects gonadotropin release from the anterior pituitary gland. In the present study we tested whether SP exerts this effect through GnRH release into pituitary portal blood in intact male rats (INT), orchidectomized rats with s.c. chronically implanted empty Silastic capsule (ORCX), testosterone capsule (ORCX + T), and 17β-estradiol capsule (ORCX + E₂). The pituitary glands were exposed by the transpharyngeal approach under urethane-chloralose anesthesia. Then, the stalk portal vessels were cut and three 30-min portal blood samples were collected. Each first sample of blood was treated as a control before 0.2 ml injection of normal saline, 5 µg, or 25 µg of SP in 0.2 ml of normal saline into the internal carotid artery. GnRH concentration in the purified portal plasma were measured by RIA. Injection of SP into the internal carotid artery caused a significant increase in GnRH concentration in pituitary portal plasma only in INT rats. The higher dose of SP markedly increased GnRH concentration in the 1st blood sample (p < 0.001) and in the 2nd blood sample GnRH concentration was lower but still significant higher than prior SP injection (p < 0.05). The lower dose of SP increased GnRH concentration later, only in the 2nd portal blood sample after intracarotid SP injection (p < 0.001). Injection of normal saline had no effect on GnRH concentration in pituitary portal blood in INT rats. In ORCX, ORCX testosterone- and estrogen-implanted rats portal plasma GnRH concentrations were not changed significantly after injection of both doses of SP. These results indicate that SP stimulates GnRH release into pituitary portal blood and the influence of SP on GnRH neurons depends on the levels of circulating gonadal steroid hormones.

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“…One is the portal vascular system (Mikkelsen et al, 1989;?sur0 et al, 1983. Another is that the moderate number of SP-immunoreactive nerve fibers present within the anterior pituitary lobe itself could have a direct action on the endocrine cells ( Ju and Liu, 1989;Muelsen et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Binding of an iodinated substance P analogue to cultured anterior pituitary prolactin- and luteinizing hormone-containing cells.

Larsen

Særmark²,

Mau³

1992

J Histochem Cytochem.

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Several lines of anatomic, biochemical, and pharmacological evidence suggest that the neuropeptide substance P has a direct action on cells of the anterior pituitary lobe via a specific neurokinin-1 receptor. In the present study we confiied this association by combining Bolton-Hunter iodinated substance Preceptor autoradiography with immunocytochemistry on cultured anterior pituitary cells. Radiolabeled substance P was bound to living cell cultures at O"C, and after a brief wash the cultures were fued and processed immunocytochemically for prolactin and luteinizing hormone. A large proportion of cultured anterior pituitary cells possessed substance P binding Sites. When receptor autoradiography was combined with immunocytochemistry, it

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Substance P in the Median Eminence and Pituitary of the Rat: Demonstration of Immunoreactive Fibers and Specific Binding Sites

Cited by 64 publications

References 16 publications

Sexually dimorphic distribution of substance P in specific anterior pituitary cell populations.

Sexually dimorphic distribution of substance P in specific anterior pituitary cell populations.

Increase of Gonadotropin-Releasing Hormone Concentration in Pituitary Portal Blood after Substance P Administration in Male Rats

Binding of an iodinated substance P analogue to cultured anterior pituitary prolactin- and luteinizing hormone-containing cells.

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