Release Of Anterior Pituitary Hormones Research Articles

Store-operated Ca2+ entry and Ca2+ responses to hypothalamic releasing hormones in anterior pituitary cells from Orai1−/− and heptaTRPC knockout mice

Store operated Ca2+ entry (SOCE) is the most important Ca2+ entry pathway in non-excitable cells. However, SOCE can also play a pivotal role in excitable cells such as anterior pituitary (AP) cells. The AP gland contains five different cell types that release six major AP hormones controlling most of the entire endocrine system. AP hormone release is modulated by Ca2+ signals induced by different hypothalamic releasing hormones (HRHs) acting on specific receptors in AP cells. TRH and LHRH both induce Ca2+ release and Ca2+ entry in responsive cells while GHRH and CRH only induce Ca2+ entry. SOCE has been shown to contribute to Ca2+ responses induced by TRH and LHRH but no molecular evidence has been provided. Accordingly, we used AP cells isolated from mice devoid of Orai1 channels (noted as Orai1−/− or Orai1 KO mice) and mice lacking expression of all seven canonical TRP channels (TRPC) from TRPC1 to TRPC7 (noted as heptaTRPC KO mice) to investigate contribution of these putative channel proteins to SOCE and intracellular Ca2+ responses induced by HRHs. We found that thapsigargin-evoked SOCE is lost in AP cells from Orai1−/− mice but unaffected in cells from heptaTRPC KO mice. Conversely, while spontaneous intracellular Ca2+-oscillations related to electrical activity were not affected in the Orai1−/− mice, these responses were significantly reduced in heptaTRPC KO mice. We also found that Ca2+ entry induced by TRH and LHRH is decreased in AP cells isolated from Orai1−/−. In addition, Ca2+ responses to several HRHs, particularly TRH and GHRH, are decreased in the heptaTRPC KO mice. These results indicate that expression of Orai1, and not TRPC channel proteins, is necessary for thapsigargin-evoked SOCE and is required to support Ca2+ entry induced by TRH and LHRH in mouse AP cells. In contrast, TRPC channel proteins appear to contribute to spontaneous Ca2+-oscillations and Ca2+ responses induced by TRH and GHRH. We conclude that expression of Orai1 and TRPC channels proteins may play differential and significant roles in AP physiology and endocrine control.

On the Neuroendocrinopathy of Critical Illness. Perspectives for Feeding and Novel Treatments.

Typical for critical illnesses are substantial alterations within the hypothalamic-anterior pituitary-peripheral hormonal axes that are proportionate to the risk of poor outcome. These neuroendocrine responses to critical illness follow a biphasic pattern. The acute phase (first hours to days) is characterized by an increased release of anterior pituitary hormones, whereas altered target-organ sensitivity and hormone metabolism result in low levels of the anabolic peripheral effector hormones and contribute to the substantially elevated levels of the catabolic hormone cortisol. The prolonged phase of critical illness is hallmarked by a uniform suppression of the neuroendocrine axes, predominantly of central/hypothalamic origin, which contributes to the low (or insufficiently high in the case of cortisol) circulating levels of the target-organ hormones. Several of the acute-phase adaptations to critical illness are due to or accentuated by the concomitant fasting. Accepting the lack of macronutrients as well as the neuroendocrine responses to such fasting in the acute phase of critical illness has shown to beneficially affect outcome. In contrast, the neuroendocrine alterations that occur in the chronic phase of illness while patients are fully fed contribute to bone and skeletal muscle wasting and impose risk of adrenocortical atrophy. The combined administration of those hypothalamic releasing factors, which have been identified as suppressed or deficient during prolonged critical illness, may be a promising strategy to enhance recovery. The potential impact of treatment with such hypothalamic releasing factors on recovery from critical illness as well as on long-term rehabilitation should be investigated in future randomized controlled clinical trials.

Synchronized Network Oscillations in Rat Tuberoinfundibular Dopamine Neurons: Switch to Tonic Discharge by Thyrotropin-Releasing Hormone

The pituitary hormone, prolactin, triggers lactation in nursing mothers. Under nonlactating conditions, prolactin secretion is suppressed by powerful inhibition from hypothalamic tuberoinfundibular dopamine (TIDA) neurons. Although firing pattern has been suggested as integral to neuroendocrine control, the electrical behavior of TIDA cells remains unknown. We demonstrate that rat TIDA neurons discharge rhythmically in a robust 0.05 Hz oscillation. The oscillation is phase locked between neurons, and while it persists during chemical synaptic transmission blockade, it is abolished by gap junction antagonists. Thyrotropin-releasing hormone (TRH) potently stimulates prolactin release, an effect assumed to take place in the pituitary. In TIDA cells, TRH caused a transition from phasic to tonic firing through combined pre- and postsynaptic effects. These findings suggest a model for prolactin regulation where a TIDA network switch from oscillations to sustained discharge converts dopamine from an antagonist at high concentrations to a functional agonist as dopamine output from the network decreases.

Potential role of type I interferons in the treatment of pituitary adenomas

Cytokines, particularly those endowed with pro-inflammatory properties, are known to influence the release of anterior pituitary hormones by a direct and indirect action at the level of pituitary gland and hypothalamus. Type I interferons (IFNs) represent a group of cytokines that act through a common receptor composed by two chains (IFNAR-1 and IFNAR-2). Several in vitro and in vivo studies underline the fact that type I IFNs are involved in the regulation of the immune-endocrine circuitry. Treatment with type I IFNs of patients affected by chronic viral hepatitis, multiple sclerosis and tumors influences the secretion of pituitary hormones. This article reviews the current knowledge about the effects of IFN-alpha and IFN-beta on hypothalamic-pituitary function and describes the potential role of type I IFNs in the treatment of pituitary adenomas.

Chronology of Advances in Neuroendocrine Immunomodulationa

This review documents the remarkable progress over the last 50 years of our knowledge of the control of anterior pituitary hormone release and synthesis by a family of peptidic releasing and inhibiting hormones, synthesized in hypothalamic neurons and released into the hypophysial portal vessels. These vessels transport them to the anterior pituitary, where they stimulate release and synthesis of pituitary hormones or inhibit these processes. In general, there are at least two hypothalamic hormones for each pituitary hormone-vasopressin and corticotrophin-releasing hormone (CRH) for adrenocorticotropin hormone (ACTH) and growth hormone-releasing hormone (GHRH) and growth hormone-inhibiting hormone (GIH) for growth hormone (GH). Some of these hormones have extrapituitary action: for example, luteinizing hormone-releasing hormone (LHRH) stimulates mating behavior. High doses of LHRH have an inhibitory action on the growth of prostate cancer. Proinflammatory and anti-inflammatory cytokines act not only in the brain, but also on the pituitary and peripheral tissues. All of these transmitters are controlled by neuronal transmitters. We anticipate further rapid progress and clinical application of these transmitters and the discovery of new ones.

In vivo and in vitro effects of chromium VI on anterior pituitary hormone release and cell viability

Hexavalent chromium (Cr VI) is a highly toxic metal and an environmental pollutant. Different studies indicate that Cr VI exposure adversely affects reproductive functions. This metal has been shown to affect several tissues and organs but Cr VI effects on pituitary gland have not been reported. Anterior pituitary hormones are central for the body homeostasis and have a fundamental role in reproductive physiology. The aim of this study was to evaluate the effect of Cr VI at the pituitary level both in vivo and in vitro. We showed that Cr VI accumulates in the pituitary and hypothalamus, and decreases serum prolactin levels in vivo but observed no effects on LH levels. In anterior pituitary cells in culture, the effect of Cr VI on hormone secretion followed the same differential pattern. Besides, lactotrophs were more sensitive to the toxicity of the metal. As a result of oxidative stress generation, Cr VI induced apoptosis evidenced by nuclear fragmentation and caspase 3 activation. Our results indicate that the anterior pituitary gland can be a target of Cr VI toxicity in vivo and in vitro, thus producing a negative impact on the hypothalamic-pituitary-gonadal axis and affecting the normal endocrine function.

Cholecystokinin Directly Inhibits Neuronal Activity of Primary Gonadotropin-Releasing Hormone Cells through Cholecystokinin-1 Receptor

Pulsatile secretion of GnRH-1 regulates gonadotropin release from anterior pituitary and thus is essential for reproduction. The present study focused on the role of cholecystokinin (CCK) in the GnRH-1 system. CCK is a neuropeptide abundantly expressed in the brain, which is implicated in activation of female reproductive behaviors and release of anterior pituitary hormones. Using dual-label immunocytochemistry coupled to confocal analysis, GnRH-1 neurons in adult mouse brain were found to express CCK-1 receptors (CCK-1R), and CCK fibers were detected contacting GnRH-1 axons. To address the function of CCK on GnRH-1 neurons, calcium imaging was used to monitor patterns of activity of GnRH-1 neurons maintained in an in vitro system known to retain many characteristics of GnRH-1 cells in vivo. Endogenous receptors for CCK (CCK-1R and CCK-2R) were blocked with selective antagonists. Results indicate that CCK-1R but not CCK-2R antagonist treatment increased the number of calcium peaks/GnRH-1 cell, mean peak amplitude, and percentage of GnRH-1 cells displaying high activity. The increased activity in GnRH-1 neurons observed after application of CCK-1R antagonist was blocked by coincubation with exogenous CCK. This study provides evidence that CCK acts directly on GnRH-1 neurons to attenuate GnRH-1 neuronal activity via CCK-1R activation.

The regulation of GH secretion by sex steroids

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.

Complement C3a receptors in the pituitary gland: a novel pathway by which an innate immune molecule releases hormones involved in the control of inflammation.

Two-way communication exists between the endocrine and immune systems using molecules such as hormones and cytokines. Here we describe a new pathway by which C3a, a complement-derived cytokine, stimulates anterior pituitary hormone release and activates the hypothalamic-pituitary-adrenal axis, a reflex central to the stress response and to the control of inflammation. We show that C3a receptors are expressed in pituitary hormone secreting and non-hormone secreting (folliculostellate) cells and that both C3a and C3adesArg (a non-inflammatory metabolite) stimulate pituitary cell cultures to release prolactin, growth hormone, and adrenocorticotropin. Serum levels of these hormones, together with adrenal corticosterone, increase dose dependently with recombinant C3a and C3adesArg administration in vivo. Pertussis toxin blocks the response to C3a but not C3adesArg, which indicates the presence of two receptors, only one of which is coupled to Galphai-proteins. We propose that the complement innate immune molecules (cytokines) modulate tissue-specific and systemic inflammatory responses through communication with the endocrine pituitary gland.

Nitric oxide decreases the production of inositol phosphates stimulated by angiotensin II and thyrotropin-releasing hormone in anterior pituitary cells.

Nitric oxide (NO) affects the synthesis of several second messengers, such as cyclic nucleotides, arachidonic acid metabolites and the intracellular calcium concentration, involved in the anterior pituitary hormone release. The present study was performed to investigate the effect of NO on phosphoinositide metabolism. The synthesis of inositol phosphates (IPs) was studied in primary cultures of anterior pituitary cells from Wistar male rats. IPs (mono, bis and tris phosphates) were determined by ionic exchange chromatography. Sodium nitroprusside and DETA NONOate (DETA/NO) significantly decreased IP synthesis and prolactin release stimulated by angiotensin II (AngII) and thyrotropin-releasing hormone (TRH). These effects were not observed with decayed DETA NONOate (unable to release NO). LY-83583, a guanylyl cyclase inhibitor, completely reversed the inhibitory effect of DETA/NO on AngII-induced IP production. However, BAY 41-2272, a novel stimulator of the soluble guanylyl cyclase, did not mimic the effect of NO donors. Likewise, neither 8-Bromine-cyclic GMP (8-Br-cGMP), an analog of cGMP, nor Sp-8-pCPT-cGMPS triethylamine, a cGMP-dependent protein kinase (PKG) stimulator, decreased IP synthesis stimulated by AngII. In addition, Rp-8-pCPT-cGMPS triethylamine, a PKG inhibitor, did not block the effect of NO. The decrease of IPs induced by DETA/NO was fully reversed by guanosine 5'-O-(3-thiotriphosphate) tetralithium salt, a non-hydrolyzable analog of GTP. The present work indicated that NO decreases IP synthesis stimulated by Ang II and TRH in anterior pituitary cells by a soluble guanylyl cyclase/cGMP/PKG-independent pathway, and suggested that NO affects some regulatory factor located between the plasma membrane receptor and G-protein.

Aberrant inflammation and resistance to glucocorticoids in annexin 1-/- mouse.

The 37-kDa protein annexin 1 (Anx-1; lipocortin 1) has been implicated in the regulation of phagocytosis, cell signaling, and proliferation and is postulated to be a mediator of glucocorticoid action in inflammation and in the control of anterior pituitary hormone release. Here, we report that mice lacking the Anx-1 gene exhibit a complex phenotype that includes an altered expression of other annexins as well as of COX-2 and cPLA2. In carrageenin- or zymosan-induced inflammation, Anx-1-/- mice exhibit an exaggerated response to the stimuli characterized by an increase in leukocyte emigration and IL-1beta generation and a partial or complete resistance to the antiinflammatory effects of glucocorticoids. Anx-1-/- polymorphonuclear leucocytes exhibited increased spontaneous migratory behavior in vivo whereas in vitro, leukocytes from Anx-1-/- mice had reduced cell surface CD 11b (MAC-1) but enhanced CD62L (L-selectin) expression and Anx-1-/- macrophages exhibited anomalies in phagocytosis. There are also gender differences in activated leukocyte behavior in the Anx-1-/- mice that are not seen in the wild-type animals, suggesting an interaction between sex hormones and inflammation in Anx-1-/- animals.

Endotoxin effects on hypothalamic gene expression in swine following sequencing of porcine c-fos mRNA

Intravenous (i.v.) endotoxin causes fever and induces cortisol and vasopressin release in prepubertal pigs. In order to investigate CNS events associated with these responses, the sequence of the porcine c-fos gene was determined. An oligonucleotide probe complementary to part of the c-fos mRNA sequence was then designed and used to examine the effect of i.v. lipopolysaccharide (LPS: 0.7 µg/kg) on gene expression in the hypothalamus. An increase in c-fos mRNA was detected in the paraventricular and supraoptic nuclei; expression was greater ( P < 0.05) than in normal animals at 30 min, but not at 120, min after LPS injection. These results are consistent with an activational effect of LPS on neuroendocrine pathways involved in the release of anterior and posterior pituitary hormones.

Stress-Induced Release of Anterior Pituitary Hormones: Effect of H3 Receptor-Mediated Inhibition of Histaminergic Activity or Posterior Hypothalamic Lesion

The effect of stress- or lipopolysaccharide (LPS) endotoxin-induced release of ACTH, β-endorphin (β-END) and prolactin (PRL) was investigated in two groups of conscious male rats: (1) Rats pretreated with different H₃ receptor agonists, which inhibit neuronal histamine (HA) synthesis and release, and (2) rats with bilateral posterior hypothalamic lesion, which destroys the histaminergic perikarya exclusively localized in the mammillary nuclei. The H₃ receptor agonists R(α)methyl-HA, BP 2-94 or imetit injected intraperitoneally (ip) had no effect on basal secretion of ACTH or PRL but inhibited the ACTH and PRL responses to restraint stress and the ACTH response to LPS endotoxin. LPS had no effect on PRL secretion. The inhibitory effect of the agonists was prevented by prior ip administration of the H₃ receptor antagonist thioperamide. Bilateral lesion of the posterior hypothalamus inhibited the ACTH, β-END and PRL responses to restraint stress, ether stress and LPS endotoxin, whereas sham operation had no effect compared to nonoperated control rats. In addition, posterior hypothalamic lesion inhibited the PRL response but not the ACTH and β-END responses to activation of serotonergic neurons induced by ip administration of the 5-HT precusor 5-hydroxytryptophan in combination with the 5-HT re-uptake inhibitor fluoxetine. Thus, serotonergic pathways were not damaged by the lesions. The present results support our previous findings that inhibition of neuronal HA synthesis by α-fluoromethylhistidine as well as blockade of H₁ or H₂ receptors inhibit the ACTH, β-END and PRL responses to stress and LPS endotoxin and further substantiate an important role of histaminergic neurons in the mediation of the stress-induced release of pituitary stress hormones. Furthermore, in accordance with our previous findings, the lesion experiments indicated the existence of an interaction between the histaminergic and serotonergic system in regulation of the stress- and LPS-induced PRL release.

Pituitary Adenylate-Cyclase-Activating Polypeptide (PACAP) Binding Sites and PACAP/Vasoactive Intestinal Polypeptide Receptor Expression in Human Pituitary Adenomas

Pituitary adenylate-cyclase-activating polypeptide (PACAP) stimulates release of several anterior pituitary hormones by interacting with PACAP receptors on pituitary cells. To learn more about the distribution and possible regulatory roles of PACAP and its receptors in human pituitary adenomas, we investigated the expression of vasoactive intestinal polypeptide (VIP) and PACAP binding sites using receptor autoradiography, PACAP and PACAP/VIP receptor (PVR) mRNAs by reverse transcription polymerase chain reaction (RT-PCR), conventional in situ hybridization, and catalyzed reporter deposition in situ hybridization (CARD-ISH) analyses. PACAP mRNA was expressed in normal human hypothalamus, which was used as a positive control, but not in pituitary adenomas. Receptor autoradiography showed PACAP types I and II binding sites in all groups of pituitary adenomas, except prolactinomas. The highest levels were present in gonadotroph and null cell adenomas. PVR-2 mRNA was expressed in normal pituitaries and in all groups of pituitary adenomas by RT-PCR, whereas PVR-1 and -3 mRNAs were expressed in all groups of pituitary adenomas, except for most prolactinomas. Conventional in situ hybridization studies with digoxigenin-labeled probes demonstrated weak staining for PVR-1, -2, and -3 mRNAs in most tissues. The CARD-ISH technique, which increased the sensitivity of the in situ hybridization method, also revealed PVR-2 mRNA expression in all adenomas, whereas PVR-1 and -3 mRNAs were detected in nearly all adenomas except for prolactinomas. The presence of PACAP mRNA in the hypothalamus, but not in normal anterior pituitary or in pituitary adenomas, and the differential expression of PVRs in adenomas indicate a selective regulatory endocrine and paracrine role of PACAP in normal and neoplastic anterior pituitary cells.

Neuropeptide Y (NPY) actions on the corticotroph cell of the anterior pituitary gland are not mediated by a direct effect

Neuropeptide Y has been implicated in the activation of the hypothalamic-pituitary-adrenal (HPA) axis, the regulation of growth and sexual function, and is the most potent stimulant of feeding yet reported. The actions of NPY on the HPA axis are thought to be mediated via an activation of the corticotrophin releasing hormone (CRH) neurones within the paraventricular nucleus of the hypothalamus. The ability of NPY to directly influence the corticotroph cell is currently controversial. These studies investigated whether NPY could have a direct influence on anterior pituitary adrenocorticotrophic hormone (ACTH) release. In dispersed male rat anterior pituitary cells, NPY (1–1000 nM) had no effect on either basal or CRH (1 nM) stimulated ACTH release. Basal release, NPY (1000 nM) 111±6% vs. control 103±5%. CRH stimulated release, CRH (1 nM) with NPY (1000 nM) 226±23% vs. CRH (1 nM) alone 228±20%. In addition, NPY (1000 nM) had no effect on either basal or CRH (1 nM) stimulated ACTH release in the mouse corticotroph cell line, AtT-20. Thus, in two models of the anterior pituitary corticotroph NPY had no effect on ACTH release. NPY induced activation of the HPA axis is likely to be mediated via a modulation of hypothalamic CRH and not via a direct action at the level of the anterior pituitary.

Hypothalamic Prolactin-Releasing Peptide Identified.

The discovery that the release of anterior pituitary hormones such as ACTH is controlled by small peptides produced in the hypothalamus won the Nobel

Role of nitric oxide in the neuroendocrine responses to cytokines.

During infection, bacterial and viral products, such as bacterial lipopolysaccharide (LPS), cause the release of cytokines from immune cells. These cytokines can reach the brain by several routes. Furthermore, cytokines, such as interleukin-1 (IL-1), are induced in neurons within the brain by systemic injection of LPS. These cytokines determine the pattern of hypothalamic-pituitary secretion which characterizes infection. IL-2, by stimulation of cholinergic neurons, activates neural nitric oxide synthase (nNOS). The nitric oxide (NO) released diffuses into corticotropin-releasing hormone (CRH)-secreting neurons and releases CRH. IL-2 also acts in the pituitary to stimulate adrenocorticotropic hormone (ACTH) secretion. On the other hand, IL-1 alpha blocks the NO-induced release of luteinizing hormone-releasing hormone (LHRH) from LHRH neurons, thereby blocking pulsatile LH but not follicle-stimulating hormone (FSH) release and also inhibiting sex behavior that is induced by LHRH. IL-1 alpha and granulocyte macrophage colony-stimulating factor (GMCSF) block the response of the LHRH terminals to NO. The mechanism of action of GMCSF to inhibit LHRH release is as follows. It acts on its receptors on gamma-aminobutyric acid (GABA)ergic neurons to stimulate GABA release. GABA acts on GABAa receptors on the LHRH neuronal terminal to block NOergic stimulation of LHRH release. This concept is supported by blockade of GMCSF-induced suppression of LHRH release from medial basal hypothalamic explants by the GABAa receptor blocker, bicuculline. IL-1 alpha inhibits growth hormone (GH) release by inhibiting GH-releasing hormone (GHRH) release, which is mediated by NO, and stimulating somatostatin release, also mediated by NO. IL-1 alpha-induced stimulation of prolactin release is also mediated by intrahypothalamic action of NO, which inhibits release of the prolactin-inhibiting hormone dopamine. The actions of NO are brought about by its combined activation of guanylate cyclase-liberating cyclic guanosine monophosphate (cGMP) and activation of cyclooxygenase and lipoxygenase with liberation of prostaglandin E2 and leukotrienes, respectively. Thus, NO plays a key role in inducing the changes in release of hypothalamic peptides induced in infection by cytokines. Cytokines, such as IL-1 beta, also act in the anterior pituitary gland, at least in part via induction of inducible NOS. The NO produced inhibits release of anterior pituitary hormones.

The Herbal Medicine Unkei‐To Stimulates Cytokine‐Induced Neutrophil Chemoattractant Production in the Pituitary Folliculo‐Stellate—Like Cell Line (TtT/GF)

We previously reported that a cytokine-induced neutrophil chemoattractant (CINC) was produced in the pituitary gland and that it influenced anterior pituitary hormone release. In this study we investigated the effect of Unkei-to, a Japanese herbal medicine, on CINC production in the rat anterior pituitary gland and the pituitary folliculo-stellate-like cell line (TtT/GF). Dispersed normal anterior pituitary cells and the folliculo-stellate-like cell line TtT/GF were used to test the effect of Unkei-to on CINC secretion and CINC mRNA accumulation. Concentrations of CINC in the conditioned media were measured by an enzyme-linked immunosorbent assay, and levels of CINC mRNA were analyzed by Northern blot analysis. Unkei-to (20 micrograms/ml) significantly increased the secretion of CINC by normal anterior pituitary cells within 12 hr of incubation. Unkei-to also stimulated CINC secretion from TtT/GF cells in a time- and dose-dependent manner. Unkei-to (20 micrograms/ml) increased CINC mRNA accumulation in TtT/GF cells within 3 hr of incubation and also caused a 13-fold increase in the secretion of CINC from TtT/GF cells compared with the vehicle group within 24 hr of incubation. Finally, we found that some of the Unkei-to's ingredients, Evodiae fructus and Pinelliae tuber, markedly stimulated CINC secretion from TtT/GF cells. Our results will help to elucidate the mechanism behind the clinical effect of Unkei-to on the anterior pituitary gland. They also suggested the presence of special substances, which stimulate CINC secretion, within Unkei-to's ingredients such as E. fructus and P. tuber.

Evidence that folliculo-stellate cells mediate the inhibitory effect of Japanese kampo medicine, unkei-to, on growth hormone secretion in rat anterior pituitary cell cultures.

Cytokine-induced neutrophil chemoattractant (CINC) was reported to influence anterior pituitary hormone release. We recently found that Unkei-to, one of the Japanese Kampo medicines, stimulated CINC secretion by rat anterior pituitary cells and the pituitary folliculo-stellate (FS)-like cell line (TtT/GF). Therefore, the effect of Unkei-to on growth hormone (GH) secretion by rat anterior pituitary cells was investigated. Dispersed normal anterior pituitary cells, the folliculo-stellate-like cell line TtT/GF, and the GH3 cell were used to test the effect of Unkei-to on GH secretion. In reconstitutive coculture experiments, TtT/GF cells were mixed with GH3 cells at a ratio (TtT/GF cells: GH3 cells) of 1:99. From this mixture, cells were seeded onto plates at a density of 10(4) cells/well and were cultured for 5 days. The cells were then used in the experiments. Unkei-to at 20 micrograms/ml significantly inhibited GH secretion by normal anterior pituitary cells within 12 hr of incubation. In contrast Unkei-to stimulated GH secretion by GH3 cells in a time- and dose-dependent manner, suggesting that an accessory cell type was involved. To assess the contribution of CINC as a paracrine factor, an experiment using a reconstitutive coculture system was performed, and Unkei-to was found to inhibit GH secretion when GH3 cells were cocultured with TtT/GF cells. The addition of anti-CINC antibody to the reconstitutive coculture system antagonized Unkei-to-inhibited GH secretion. CINC, which was secreted from FS cells by Unkei-to, may be responsible for mediating the inhibitory effect of Unkei-to on GH secretion by rat anterior pituitary cells.

Norepinephrine Content in the Paraventicular Nucleus of the Hypothalamus as a Function of Photoperiod and Dopaminergic Tone

The decline in the release of various anterior pituitary hormones, particularly prolactin (PRL), as a result of exposure to inhibitory, short-day photoperiods in long-day breeders is a well-documented phenomenon. This alteration in the hypothalamic-hypophyseal-gonadal axis is largely controlled by changes in the duration of the nocturnal melatonin pulse secreted by the pineal gland. Increased duration of melatonin secretion serves to increase the inhibitory activity of the tuberoinfundibular dopaminergic (TIDA) neurons, which in turn suppress PRL release and synthesis. However, other hypothalamic factors also appear to stimulate anterior pituitary function, working in concert with changes in TIDA activity to modulate circulating PRL levels under different photoperiod conditions. Past work from this laboratory has suggested that neurochemical changes at the level of the hypothalamic paraventricular nuclei (PVN), particularly changes in norepinephrine (NE) activity, may represent one of these modulatory influences. The current study investigated potential alterations in NF, content within the PVN during the early stages of short-day exposure in Siberian hamsters. In addition, the interaction of NE content with the modulatory dopamine (DA) system was investigated via administration of a DA agonist (CD154) or antagonist (pimozide). Hamsters received CB 154 (500 micrograms), pimozide (45 micrograms), or control solution via the drinking water under either long days (16L:8D) or short days (10L:14D), and were sacrificed at 1, 3, or 5 wk of photoperiod and drug treatment. The brains were removed, and the PVN microdissected from the hypothalamus and analyzed for catecholamine content using high-pressure liquid chromatography with electrochemical detection (HPLC-EC). The results revealed the expected stimulation of circulating PRL under both photoperiods following pimozide administration, as well as the expected trend toward an accelerated suppression of PRL under short days induced by CB 154. For control animals, there were no changes in NE content, or the ratio of 3-methoxy-4-hydroxyphenyglycol (MHPG)/ NE in long-day exposed animalx, but for short-day animals, both NE content and the ratio of MHPG/NE declined over time. Administration of CB 154 had only a marginal effect on NE content and the ratio of MHPG/ NE, but pimozide administration resulted in a decline in NE content and an increase in the MHPG/NE ratio under short days, and an increase in NE content and the MHPG/NE ratio over time for long-day animals. These results suggest that both photoperiod and administration of a DA antagonist that increases circulating PRL levels induce alterations in NE terminal activity within the hypothalamic PVN.