The TRH test provides valuable information in the diagnosis of central hypothyroidism in patients with known pituitary disease and low T4 levels.

Objective: To evaluate the value of the thyrotropin-releasing hormone (TRH) test in the diagnosis of central hypothyroidism (CH) in patients with pituitary disease. Methods: Systematic evaluation of 359 TRH tests in patients with pituitary disease including measurements of thyroxine (T4), TBG-corrected T4 (T4corr), baseline TSH (TSH0) and relative or absolute TSH increase (TSHfold, TSHabsolute). Results: Patients diagnosed with CH (n=39) show comparable TSH0 (p-value 0.824) but lower T4corr (p-value <0.001) and lower TSH increase (p-value <0.001) compared to patients without CH. In 54% (42 of 78 cases) of patients with low T4corr, the CH diagnosis was rejected based on a high TSHfold. In these cases, a spontaneous increase and mean normalization in T4corr (from 62 to 73 nmol/L, p-value <0.001) was observed during the follow-up period (7.6 ± 5.0 years). Three of the 42 patients (7%) were started on replacement therapy due to spontaneous deterioration of thyroid function after 2.8 years. Patients diagnosed with CH reported significantly more symptoms of hypothyroidism (p-value 0.005), although, symptoms were reported in most patients with pituitary disease. The TRH test did not provide clinical relevant information in patients with normal T4 or patients awaiting pituitary surgery (78%, 281 of 359). There were only mild and reversible adverse effects related to the TRH test except for possibly one case (0.3%) experiencing a pituitary apoplexy. Conclusion: The TRH test could be reserved to patients with pituitary disease, low T4 levels without convincing signs of CH. Approximately 50% of patients with a slightly decreased T4 were considered to have normal pituitary thyroid function based on the TRH test results.

Filtered air intervention modulates hypothalamic-pituitary-thyroid/gonadal axes by attenuating inflammatory responses in adult rats after fine particulate matter (PM2.5) exposure.

We have previously reported that filtered air (FA) intervention reduces inflammation and hypothalamus-pituitary-adrenal axis activation after fine particulate matter (PM2.5 exposure). Whether FA also modulates the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) axes in rats after PM2.5 exposure is still unknown. Adult Sprague-Dawley rats were exposed to PM2.5 by using a "real-world" PM2.5 exposure system, and the FA intervention was conducted by renewing for 15 days. PM2.5 inhalation decreased thyrotropin-releasing hormone (TRH) and thyroxine (T4) levels in both male and female rats, and thyroid-stimulating hormone (TSH) level in male rats. FA intervention attenuated the reduction in TRH and TSH levels in male rats and reduction in T4 level in female rats. PM2.5 inhalation also reduced testosterone (T) level in male rats, and estradiol (E2) and progesterone (PROG) levels in female rats, and these changes were attenuated after FA intervention. The FA intervention attenuated the decreases in CD8 T cells and T cells induced by PM2.5 inhalation in female rats only by flow cytometry analysis. In blood, FA interventions ameliorated IL-6 and IL-1ß mRNA levels in both male and female rats after PM2.5 exposure. FA intervention restored the IL-4 and IL-10 levels in female rats after PM2.5 exposure. Moreover, FA intervention ameliorated the inflammatory responses induced by PM2.5 inhalation in the thyroid and gonads in both male and female rats. These data indicate that FA intervention exerted an effect on modulating the hormonal balance of the HPT and HPG axes, and this may be related to a reduction in the inflammatory responses in the thyroid and gonads of PM2.5-treated rats, respectively.

Are the thyroid and adrenal system alterations linked in depression?

BACKGROUND: Disturbances in the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-adrenal (HPA) axes have been frequently found in major depression. Given that glucocorticoids may inhibit thyrotropin (TSH) and thyrotropin-releasing hormone (TRH) secretion, it has been hypothesized that hypercortisolemia could lead to HPT axis abnormalities. So far, data on interactions between the HPA and HPT axes in depression remain inconclusive. METHODS: In order to investigate this issue, we examined circadian rhythms of serum TSH and cortisol (sampled at 4 -hly intervals throughout a 24 -h span), TSH responses to 0800 h and 2300 h protirelin (TRH) tests and cortisol response to dexamethasone suppression test (DST) in 145 unmedicated inpatients meeting DSM-IV criteria for major depressive disorder (MDDs) and 25 healthy hospitalized control subjects (HCs). RESULTS: The secretion of TSH and cortisol exhibited a significant circadian rhythm both in HCs and MDDs. However, compared to HCs, MDDs showed: 1) reduced TSH mesor and amplitude values; 2) blunted 2300 h-ΔTSH and ΔΔTSH values (i.e. differences between 2300 h and 0800 h TRH-TSH responses); and 3) increased cortisol mesor and post-DST cortisol values. DST nonsuppresssors (n = 40, 27 %) showed higher cortisol mesor than DST suppressors (n = 105, 73 %). There was no difference between DST suppressors and nonsuppressors in their TSH circadian parameters and TRH-TSH responses. In addition, cortisol values (circadian and post-DST) were not related to TRH test responses. CONCLUSION: Our results do not confirm a key role for hypercortisolemia in the HPT axis dysregulation in depression.

Pituitary Gangliocytoma Producing TSH and TRH: A Review of "Gangliocytomas of the Sellar Region".

PURPOSE: Pituitary gangliocytomas (GCs) are rare neuronal tumors that present with endocrinological disorders, such as acromegaly, amenorrhea-galactorrhea syndrome, and Cushing's disease. Most pituitary GCs coexist with pituitary adenomas pathologically and are diagnosed as mixed gangliocytoma-adenomas. Herein, we report a case of 45-year-old man who presented with the syndrome of inappropriate secretion of thyroid-stimulating hormone (SITSH) and discuss the pathogenesis of pituitary GCs. METHODS: Pituitary magnetic resonance imaging showed an 8-mm homogeneous and poorly enhanced mass inside the pituitary gland. Endoscopic transsphenoidal surgery was performed under a preoperative diagnosis of thyrotroph adenoma. However, the tumor was finally diagnosed as gangliocytoma without an adenomatous component. The tumor was further analyzed via immunohistochemistry and electron microscopy. Additionally, we searched MEDLINE and PubMed for previously published cases of isolated pituitary GCs and analyzed the reported clinicopathological findings. RESULTS: The patient showed complete clinical and endocrinological recovery after an operation. The tumor was positive for thyrotropin (TSH), TSH-releasing hormone (TRH), Pit-1, GATA-2, and most neuronal markers. Electron microscopy demonstrated the presence of intracytoplasmic secretory granules and neuronal processes. Co-secreting hypothalamic and pituitary hormone inside the tumor indicated autocrine/paracrine endocrinological stimulation. CONCLUSION: Herein, we report a case of SITSH caused by an isolated pituitary gangliocytoma, expressing both TSH and TRH, which, to our best knowledge, is the first reported case of such a condition. The multidirectional differentiation and multihormonal endocrine characteristics of these tumors indicate that they are a member of neuroendocrine neoplasms, further supporting that they are derived from neural crest cells.

Target-controlled liposome amplification for versatile nanopore analysis.

We have reported a versatile nanopore method based on the combination of analyte-controlled liposome signal amplification and the nanopore detection of a reporter molecule, which largely extends the nanopore application range, and easily elevates the nanopore sensitivity to the fM level from the µM level.

Use of the TRH Stimulation Test to Assess Long Term Changes of Thyroid Function in an Olympic Athlete.

This case report presents the utility of the thyroid-releasing hormone (TRH) stimulation test for assessing endocrine disease in athletes. On two occasions, 4 years apart (1992 and 1996), a TRH stimulation test was performed to corroborate clinical symptoms and observation. On the first occasion, the patient's symptoms were not attributed to thyroid disease. He was treated for a sinus infection with amoxicillin/clavulanate 500 mg three times per day for 1 wk. On the second occasion, thyroid disease was confirmed and treatment with 100-µg L-thyroxine was initiated. Baseline screening and TRH stimulation testing were used at both assessment time points. Baseline screen for TSH was 2.2 and 1.2 uUI·mL and stimulated TSH was at 15.2 uUI·mL at 30 min and 30.6 uUI·mL at 45 min for the first (1992) and second (1996) assessment, respectively. Patient was positive on the second visit for antithyroglobulin antibodies at 70 IU·mL (normal, 0-59 IU·mL). Three months postdiagnosis, TSH was 0.66 uIU·mL and the patient was asymptomatic. At the most recent visit, 20 years and 4 months later, no symptomology was reported and TSH was 0.55 uIU·mL A greater understanding of the interaction between stress and end organ function is warranted in occupations undergoing unique stressors.

Development of pituitary apoplexy during TRH/GnRH test in a patient with pituitary macroadenoma.

Pituitary apoplexy occurs as a very rare complication following pituitary function tests. Signs and symptoms are due to the rapid expansion of an infarcted and/or haemorrhagic pituitary adenoma. We report a case of macroadenoma, in which pituitary apoplexy developed 30 minutes after administration of thyrotropin-releasing hormone (TRH) and gonadotropin-releasing hormone (GnRH) injections. Magnetic resonance (MR) imaging had earlier revealed several haemorrhagic zones. After the TRH and GnRH injections, the patient complained of visual defect. MR imaging demonstrated an increase in the size of the pituitary adenoma and several haemorrhagic zones that formed a fluid-fluid level at the centre of the lesion. The pituitary mass was removed using the transsphenoidal approach. On immunostaining, follicle-stimulating and luteinising hormones were strongly positive, while prolactin was weakly positive. Pituitary functions were evaluated by dynamic function tests at six weeks post operation. The patient's pituitary functions and visual acuity were found to be normal.

Quantification of thyrotropin-releasing hormone by liquid chromatography-electrospray mass spectrometry.

Thyrotropin-releasing hormone (TRH) is involved in a wide range of biological responses. It has a central role in the endocrine system and regulates several neurobiological activities. In the present study, a rapid, sensitive and selective liquid chromatography-mass spectrometry method for the identification and quantification of TRH has been developed. The methodology takes advantage of the specificity of the selected-ion monitoring acquisition mode with a limit of detection of 1 fmol. Furthermore, the MS/MS fragmentation pattern of TRH has been investigated to develop a selected reaction monitoring (SRM) method that allows the detection of a specific b2 product ion at m/z 249.1, corresponding to the N-terminus dipeptide pyroglutamic acid-histidine. The method has been tested on rat hypothalami to evaluate its suitability for the detection within very complex biological samples.

Utilidad de la determinación de la subunidad alfa tras estímulo con TRH como indicador de persistencia y/o recurrencia tumoral en gonadotropinomas / Utility of alpha subunit determination alter thyrotropin-releasing hormone stimulation as an indicator of gonadotropinoma persistente and/or recurrence

Objetivo: Los gonadotropinomas son tumores originados en las células gonadotropas de la hipófisis anterior causales de la síntesis y la secreción de gonadotrofinas (folitropina [FSH] y lutropina [LH]). La mayoría de estos tumores tienen una producción alterada de gonadotropinas y de sus subunidades (folitropina beta, subunidad alfa y, con menos frecuencia, lutropina beta). Los gonadotropinomas pueden presentar una respuesta de la subunidad alfa de las gonadotropinas al estímulo con protirrelina (TRH) que podría diferenciar estos tumores de los no funcionantes. De igual forma, esta prueba podría ser de utilidad tras la cirugía para poderdiscernir los posibles restos tumorales respecto a los cambios posquirúrgicos. Sujetos y método: Se estudió a 24 pacientes intervenidos de macroadenoma hipofisario, de los que 14 fueron diagnosticados de gonadotropinoma en el estudio histológico. Se les practicó la prueba de lasubunidad alfa tras la administración de TRH antes y después de la cirugía.Resultados: En el estudio prequirúrgico el 50% de los gonadotropinomas tuvieron una respuesta positiva a dicha prueba y en el posquirúrgico otro 50%. El 83% de los pacientes con gonadotropinoma presentaban signos de recidiva/persistencia tumoral y/o cambios en laresonancia magnética (RM) de control posquirúrgico; el 83% de estos pacientes (41,6% del total) tuvo una respuesta positiva de la subunidad alfa tras el estímulo con TRH. En el grupo de macroadenomas no gonadotropinomas sólo un 33% tuvo respuesta positiva antes de la cirugía y otro 33%, después. En la RM practicada después de la cirugía, todos mostraban signos radiológicos compatibles con cambios inflamatorios posquirúrgicos o signos de persistencia y/o recidivatumoral. Conclusiones: Dicha prueba podría ser de ayuda en el diagnóstico diferencial de los gonadotropinomas, así como en el seguimiento y la valoración posquirúrgica de estos tumores (AU)

Objective: Gonadotropinomas are adenomas of the gonadotropic cells of the anterior pituitary. These cells produce and secrete gonadotropins (follicle-stimulating hormone and luteinizing hormone). Most of these tumors show altered production of gonadotropins and their subunits (the - FSH, and, less frequently, -LH subunits). The thyrotropin-releasing hormone (TRH) stimulation test could differentiate these tumors from nonfunctioning tumors. Equally, this test could be able to distinguish between postsurgical changes and tumoral remnants after surgery. Subjects and method: We studied 24 patients with pituitary macroadenoma, 14 of who had a histological diagnosis of gonadotroph adenoma. The TRH stimulation test was performed before and after surgery. Results: Both before and after surgery, a positive result to the TRH test was obtained in 50% of gonadotropinomas. Magnetic resonance imaging (MRI)performed after surgery revealed that 83% of the patients with gonadotropinoma had signs of tumoral persistence or recurrence and/or postsurgical changes. Of these patients, 83% (41.6% of the total) showed positive (..) (AU)

Escitalopram regulates expression of TRH and TRH-like peptides in rat brain and peripheral tissues.

BACKGROUND: Escitalopram (eCIT) is a highly selective serotonin reuptake inhibitor (SSRI) that can be an effective treatment for a number of neuropsychiatric disorders including major depression. We, and others, have previously reported that thyrotropin-releasing hormone (TRH, pGlu-His-Pro-NH(2)) and TRH-like peptides with the general structure pGlu-X-Pro-NH(2), where 'X' can be any amino acid residue, have neuroprotective, antidepressant, analeptic, arousal, and anti-epileptic effects that could mediate the neuropsychiatric and therapeutic effects of a variety of neurotropic agents. The present work explores the possible mediation of the therapeutic effects of eCIT by TRH and TRH-like peptides. METHODS: In order to extend our understanding of the range of neurotransmitter systems that are modulated by and, in turn, influence the expression of TRH and TRH-like peptides, 16 male Sprague-Dawley rats were injected i.p. with eCIT (24 mg/kg BW) and the brain levels of TRH and TRH-like peptides in various brain regions involved in mood regulation and peripheral tissues with serotonergic innervation were measured 0, 2, 4, and 6 h later by combined HPLC and RIA. RESULTS AND CONCLUSION: Remarkable 3- to 25-fold increases in TRH and TRH-like peptide levels were observed 2 h after i.p. eCIT in the epididymis. This reproductive tissue has the highest level of serotonin found in most mammals. The acute (2 h) effect of eCIT in brain regions involved in mood regulation, particularly the nucleus accumbens and medulla oblongata, cerebellum, and striatum was to increase the levels of TRH-like peptides, most consistently Phe-TRH. An important exception was a decrease in the level of TRH in the nucleus accumbens. These responses, in general, were the opposite of those we have previously observed after acute restraint stress in this same rat strain. We conclude that some of the therapeutic effects of inhibition of serotonin reuptake are mediated by altered release of TRH and TRH-like peptides.

Thyroid hormone status and pituitary function in adult rats given oral doses of perfluorooctanesulfonate (PFOS).

INTRODUCTION: Perfluorooctanesulfonate (PFOS) is widely distributed and persistent in humans and wildlife. Prior toxicological studies have reported decreased total and free thyroid hormones in serum without a major compensatory rise in thyrotropin (TSH) or altered thyroid gland histology. Although these animals (rats, mice and monkeys) might have maintained an euthyroid state, the basis for hypothyroxinemia remained unclear. We undertook this study to investigate the causes for the PFOS-induced reduction of serum total thyroxine (TT4) in rats. HYPOTHESES: We hypothesized that exposure to PFOS may increase free thyroxine (FT4) in the rat serum due to the ability of PFOS to compete with thyroxine for binding proteins. The increase in FT4 would increase the availability of the thyroid hormone to peripheral tissues for utilization, metabolic conversation, and excretion. We also hypothesized that PFOS does not directly interfere with the regulatory functions of the hypothalamic-pituitary-thyroid (HPT) axis in rats. EXPERIMENTS: Three experimental designs were employed to test these hypotheses. (1) Female Sprague-Dawley (SD) rats were given a single oral dose of 15 mg potassium PFOS/kg body weight. At intervals of 2, 6, and 24h thereafter, measurements were made for serum FT4, TT4, triiodothyronine (TT3), reverse triiodothyronine (rT3), thryrotropin (TSH), and PFOS concentrations, as well as liver PFOS concentrations, UDP-glucuronosyltransferase 1A (UGT1A) family mRNA transcripts, and malic enzyme (ME) mRNA transcripts and activity. (2) To provide evidence for increased uptake and metabolism of thyroxine (T4), 125 I-T4 was given to male and female SD rats by intravenous injection, followed in 2h by a single oral dose of 15 mg potassium PFOS/kg body weight. 125 I radioactivity was determined in urine and feces collected over a 24-h period and in serum and liver collected at 24h. (3) To assess the potentials effect of PFOS on the hypothalamic-pituitary-thyroid axis, over an 8-day period, groups of male SD rats were given PFOS (3mg/kg-d), propyl thiouracil (PTU, 10 microg/mL in water), or PTU and PFOS in combination, with controls receiving 0.5% Tween 20 vehicle. On days 1, 3, 7, and 8, TT4, TT3, and TSH were monitored. On day 8, pituitaries were removed and placed in static culture for assessment of thyrotropin releasing hormone (TRH)-mediated release of TSH. RESULTS: (1) PFOS transiently increased FT4 and decreased TSH within 6h, with values returning to control levels by 24h. TT4 was decreased by 55% over a 24-h period. TT3 and rT3 were decreased at 24h to a lesser extent than TT4. ME mRNA transcripts were increased at 2h and activity was increased at 24h. UGT1A mRNA transcripts were increased at 2 and 6h. (2) 125 I decreased in serum and liver relative to controls and consistent with a reduction in serum TT4. Concomitantly, 125 I activity was increased in urine and feces collected from PFOS-treated rats. (3) During the 8 days of dosing with PFOS, TSH was not elevated in male rats, while TT4 and TT3 were decreased. Pituitary response to TRH-mediated TSH release was not diminished after 8-daily oral doses of PFOS. CONCLUSIONS: These findings suggest that oral dosing in rats with PFOS results in transiently increased tissue availability of the thyroid hormones and turnover of T4 with a resulting reduction in serum TT4. PFOS does not induce a classical hypothyroid state under dosing conditions employed nor does it alter HPT activities.

Diagnóstico bioquímico del exceso de secreción de prolactina / Biochemical diagnosis of prolactin secretion excess

La prolactina actúa principalmente en la glándula mamaria iniciando y manteniendo la lactación. El exceso de secreción de prolactina se presenta tanto en varones como en mujeres y se manifiesta clínicamente por disfunciones sexuales o reproductivas o galactorrea. En los casos en que se detecta hiperprolactinemia, el principal objetivo es demostrar o descartar la presencia de un adenoma hipofisario secretor de prolactina. Para valorar la normalidad de la secreción de la hormona son suficientes, en general, las determinaciones basales de prolactina y no se requiere de pruebas de estimulación o frenación para establecer o confirmar el diagnóstico bioquímico. Es preciso controlar estrictamente las condiciones de extracción de la muestra para poder valorar correctamente los resultados. En individuos sanos, la prolactina circula en la sangre en tres formas moleculares; una de ellas es un complejo antígeno-anticuerpo formado por la prolactina y una inmunoglobulina de la clase IgG, denominado macroprolactina, que, aunque tiene una actividad biológica limitada y menor biodisponibilidad que la forma monomérica, es inmunorreactiva y produce resultados de prolactina por encima del intervalo de referencia en el 10-15% de los casos de hiperprolactinemia. Para detectar la macroprolactina se utiliza, generalmente, un método basado en la precipitación de las proteínas con polietilenglicol

Prolactin (PRL) acts mainly on the mammary gland, initiating and maintaining lactation. Excess PRL secretion occurs in both men and women and manifests clinically with sexual or reproductive dysfunction or galactorrhea. When hyperprolactinemia is detected, the main aim is to establish or rule out the presence of a PRL-secreting pituitary adenoma. In general, hormone secretion levels can be evaluated using baseline PRL determinations without the need for stimulation or suppression tests to establish or confirm the biochemical diagnosis. The conditions under which the blood sample is extracted must be strictly controlled for correct interpretation of the results. In healthy individuals, PRL circulates in blood in three molecular forms, one of which is an antigen-antibody complex composed of PRL and an IgG immunoglobulin called macroprolactin. Although the biological activity and bioavailablity of macroprolactin is more limited than those of the monomeric form, this complex is immunoreactive and produces PRL levels that are above the reference range in 10-15% of individuals with hyperprolactinemia. To detect macroprolactin, a method based on polyethylene glycol precipitation is generally used

Electroconvulsive seizure-induced gene expression profile of the hippocampus dentate gyrus granule cell layer.

Electroconvulsive shock (ECS) is the most effective treatment for depression, but the mechanism underlying the therapeutic action of this treatment is still unknown. To better understand the molecular changes that may be necessary for the clinical effectiveness of ECS we have combined the technologies of gene expression profiling using cDNA microarrays with T7-based RNA amplification and laser microdissection to identify regulated genes in the dentate gyrus granule cell layer of the hippocampus. We have identified genes previously reported to be up-regulated following ECS, including brain-derived neurotrophic factor, neuropeptide Y, and thyrotrophin releasing hormone, as well as several novel genes. Notably, we have identified additional genes that are known to be involved in neuroprotection, such as growth arrest DNA damage inducible beta (Gadd45beta), and the excitatory amino acid transporter-1 (EAAC1/Slc1A1). In addition, via in situ hybridization we show that EAAC1 is specifically up-regulated in the dentate gyrus, but not in other hippocampal subfields. This study demonstrates the utility of microarray analysis of microdissected subregions of limbic brain regions and identifies novel ECS-regulated genes.

Cloning and hypothalamic distribution of the chicken thyrotropin-releasing hormone precursor cDNA.

In this paper we report the cloning of the chicken preprothyrotropin-releasing hormone (TRH) cDNA and the study of its hypothalamic distribution. Chicken pre-proTRH contains five exact copies of the TRH progenitor sequence (Glu-His-Pro-Gly) of which only four are flanked by pairs of basic amino acids. In addition, the amino acid sequence contains three sequences that resemble the TRH progenitor sequence but seem to have lost their TRH-coding function during vertebrate evolution. The amino acid sequence homology of preproTRH between different species is very low. Nevertheless, when the tertiary structures are compared using hydrophobicity plots, the resemblance between chicken and rat prepro-TRH is striking. The cloning results also showed that the chicken preproTRH sequence includes neither a rat peptide spacer 4 (Ps4) nor a Ps5 connecting peptide. Comparison of the cDNA sequence with the chicken genome database revealed the presence of two introns, one in the 5' untranslated region, and another downstream from the translation start site. This means that the gene structure of chicken preproTRH resembles the gene stucture of this precursor in mammals. Based on the cDNA sequence, digoxigenin-labelled probes were produced to study the distribution of preproTRH in the chicken brain. By means of in situ hybridization, preproTRH mRNA was detected in the chicken paraventricular nucleus (PVN) and in the lateral hypothalamus (LHy).

Online preconcentration of thyrotropin-releasing hormone (TRH) by SDS-modified reversed phase column for microbore and capillary high-performance liquid chromatography (HPLC).

Thyrotropin-releasing hormone (TRH, pGlu-His-Pro-amide) is an important tripeptide existing in biological systems at low concentrations. It is a fairly hydrophilic peptide, cationic in acidic solutions. Preconcentration online before reversed phase chromatography separation can enhance concentration detection limits of hydrophobic, but not hydrophilic species. The hydrophilic TRH can be preconcentrated using a reversed phase precolumn charged with sodium dodecyl sulfate (SDS). The separation also uses SDS. The preconcentration is effective for a microbore system, achieving detection limit of 250 pM for a sample size of 500 microl with electrochemical detection of the biuret complex formed post column. Preconcentration using an online precolumn is also effective in packed capillary high-performance liquid chromatography (HPLC) with a detection limit of 3 nM in 24 microl.

Excitatory effects of thyrotropin-releasing hormone in the thalamus.

The activity of the thalamus is state dependent. During slow-wave sleep, rhythmic burst firing is prominent, whereas during waking or rapid eye movement sleep, tonic, single-spike activity dominates. These state-dependent changes result from the actions of modulatory neurotransmitters. In the present study, we investigated the functional and cellular effects of the neuropeptide thyrotropin-releasing hormone (TRH) on the spontaneously active ferret geniculate slice. This peptide and its receptors are prominently expressed in the thalamic network, yet the role of thalamic TRH remains obscure. Bath application of TRH resulted in a transient cessation of both spindle waves and the epileptiform slow oscillation induced by application of bicuculline. With intracellular recordings, TRH application to the GABAergic neurons of the perigeniculate (PGN) or thalamocortical cells in the lateral geniculate nucleus resulted in depolarization and increased membrane resistance. In perigeniculate neurons, this effect reversed near the reversal potential for K+, suggesting that it is mediated by a decrease in K+ conductance. In thalamocortical cells, the TRH-induced depolarization was of sufficient amplitude to block the generation of rebound Ca2+ spikes, whereas the even larger direct depolarization of PGN neurons transformed these cells from the burst to tonic, single-spike mode of action potential generation. Furthermore, application of TRH prominently enhanced the afterdepolarization that follows rebound Ca2+ spikes, suggesting that this transmitter may also enhance Ca2+-activated nonspecific currents. These data suggest a novel role for TRH in the brain as an intrinsic regulator of thalamocortical network activity and provide a potential mechanism for the wake-promoting and anti-epileptic effects of this peptide.

Expression of thyrotropin-releasing hormone by human melanoma and nevi.

PURPOSE: Thyrotropin-releasing hormone (TRH) is a tripeptide hormone produced by the hypothalamus in response to hypothyroidism. RNA transcripts for the TRH prohormone have recently been described in melanoma cell lines. To expand these findings, we have examined cultured melanoma cells and melanocytes, human melanoma tumors, and nevi for the expression of TRH. EXPERIMENTAL DESIGN: Five melanoma cell lines were analyzed by reverse transcription-PCR/Southern blotting for preproTRH message. The same melanoma lines and two melanocyte lines were examined by immunocytochemistry for TRH protein expression and for growth response to exogenous TRH. Immunohistochemistry was used to test for TRH protein in sections of 19 melanomas, 33 dysplastic nevi, and 27 benign nevi. RESULTS: TRH message and protein were detected in all melanoma cell lines examined. Melanocytes were also found to express TRH protein. Four of the five melanoma cell lines but neither melanocyte line responded with a increase in proliferation to low concentrations of exogenous TRH. TRH immunoreactivity was observed in 12 of 19 melanomas (63%), 23 of 33 (69.7%) dysplastic nevi, and 14 of 27 (51.9%) benign nevi. Expression in dysplastic nevi was significantly greater than in benign nevi. Upon separate analysis of nevi from melanoma patients, the difference between dysplastic and benign nevi was even more significant. However, in healthy individuals, no difference between dysplastic and benign nevi was observed. Furthermore, dysplastic nevi from melanoma patients had a significantly higher percentage of TRH-positive cells when compared with healthy individuals. CONCLUSIONS: TRH is commonly expressed by melanomas and dysplastic nevi and may function as a melanoma autocrine growth factor. The presence of TRH in dysplastic nevi may be predictive for the development of melanoma. Our findings have significant clinical and biological implications for future research into the early stages of melanoma initiation and progression.

Galanin- but not galanin-like peptide-containing axon terminals innervate hypophysiotropic TRH-synthesizing neurons in the hypothalamic paraventricular nucleus.

Galanin and galanin-like peptide (GALP) are both orexigenic peptides involved in the regulation of food intake and energy metabolism. To determine whether these peptides may directly influence the hypophysiotropic thyrotropin-releasing hormone (TRH)-synthesizing neurons, double-labeling immunocytochemistry was performed at light and electron microscopic levels using antisera against proTRH, galanin and GALP. Galanin-IR axons densely innervated all of the major parvocellular subdivisions of the PVN where proTRH neurons were identified. The periventricular and anterior parvocellular subdivisions exhibited a prominent network of galaninergic nerve fibers, while the density of fibers was less intense in the medial parvocellular subdivision. Galanin-immunoreactive (IR) axon varicosities were juxtaposed to the majority of TRH-synthesizing neurons in the anterior, medial and periventricular subdivisions of the PVN. Ultrastucturally, galanin-IR nerve terminals established symmetric type synapses with the perikarya of proTRH-IR neurons, suggesting an inhibitory nature of these contacts. In contrast, GALP immunoreactive fibers and nerve terminals concentrated primarily in the anterior parvocellular subdivision of the PVN and were found in association with only few proTRH-IR neurons in the periventricular and medial parvocellular subdivisions. In conclusion, the dense innervation of TRH neurons in all subdivisions of the PVN by galanin-IR axons indicates that galanin may be involved in the central regulation of the hypothalamic-pituitary-thyroid axis. In contrast, the relative paucity of GALP-containing axons in juxtapsoition to TRH neurons in the medial and periventricular parvocellular subdivisions of the PVN, the origin of hypophysiotropic TRH neurons, makes it unlikely that GALP similarly exerts direct regulatory effects on hypophysiotropic TRH neurons.

[Effect of endotoxemia on thyrotropin releasing hormone and its receptor in Wistar rat brain].

OBJECTIVE: To study the dose and location of thyrotropin releasing hormone (TRH) and its receptor in Wistar rat's brain when early endotoxemia happened. METHODS: Twenty-two Wistar rats were selected. In 13 mouse the model was established with endotoxemia and hemorrhagic shock. The TRH and its receptor were observed with radioimmunoassay (RIA), and were compared to the 9 control rats. RESULTS: The dose of TRH decreased significantly in the early stage of endotoxemia. The maxium dose (Bmax) of TRH increased while Kd (affinity) decreased, so the effective TRH receptor had no significantly change. CONCLUSION: The dose of TRH is different in brain and serum. The decrease of TRH and the steady of active TRH receptor may protect the brain tissue and repress multiple organ dysfunction syndrome (MODS) in the early stage of endotoxemia.

Central administration of neuropeptide Y reduces alpha-melanocyte-stimulating hormone-induced cyclic adenosine 5'-monophosphate response element binding protein (CREB) phosphorylation in pro-thyrotropin-releasing hormone neurons and increases CREB phosphorylation in corticotropin-releasing hormone neurons in the hypothalamic paraventricular nucleus.

Neuropeptide Y (NPY) has a potent inhibitory effect on TRH gene expression in the paraventricular nucleus (PVN) and contributes to the fall in circulating thyroid hormone levels during fasting mediated by a reduction in serum leptin levels. Because alpha-MSH activates the TRH gene by increasing the phosphorylation of CREB in the nucleus of these neurons, we raised the possibility that at least one of the mechanisms by which NPY reduces TRH mRNA in hypophysiotropic neurons is by antagonizing the ability of alpha-MSH to phosphorylate CREB. As NPY increases CRH mRNA in the hypothalamus, we further determined whether intracerebroventricular (i.c.v.) administration of NPY regulates the phosphorylation of CREB in hypophysiotropic CRH neurons. NPY [10 micro g in artificial CSF (aCSF)] was administered into the lateral ventricle i.c.v. 30 min before the i.c.v. administration of aCSF or alpha-MSH (10 micro g in aCSF), the latter in a dose previously demonstrated to increase proTRH mRNA and phosphorylate CREB in TRH neurons. By double-labeling immunocytochemistry, only few TRH neurons in the PVN contained phosphoCREB (PCREB) in animals treated only with aCSF (4 +/- 0.2%) or with NPY followed by aCSF (9.7 +/- 2.5), whereas alpha-MSH-infused animals dramatically increased the percentage of TRH neurons containing PCREB (75.3 +/- 6.9%). Pretreatment with NPY before alpha-MSH infusion, however, significantly reduced the percentage of TRH neurons containing PCREB (40.8 +/- 3.5%) compared with alpha-MSH infused animals (P = 0.01). Only 12.2 +/- 0.9% of CRH neurons of the medial parvocellular neurons contained PCREB nuclei in vehicle-treated animals, whereas 30 min following NPY infusion, the number of CRH neurons containing PCREB increased dramatically to 88 +/- 2.9%. Whereas alpha-MSH infusion increased the percentage of CRH neurons that contained PCREB to 56 +/- 2.2% compared with control, animals pretreated with NPY further increased the number of CRH neurons colocalizing with PCREB to 87 +/- 2.5%. These data demonstrate a functional interaction between NPY and alpha-MSH in the regulation of proTRH neurons in the PVN, suggesting that NPY can antagonize alpha-MSH induced activation of the TRH gene by interfering with melanocortin signaling at the postreceptor level, preventing the phosphorylation of CREB. In contrast, NPY infusion increases the phosphorylation of CREB in CRH neurons, indicating that NPY has independent effects on discrete populations of neurons in the PVN, presumably mediated through different signaling mechanisms.