Successful treatment of repeated hematemesis secondary to postsclerotherapy esophageal ulcer in a cirrhotic patient: A case report.

Esophageal variceal bleeding is a common lethal complication of cirrhosis. Endoscopic injection sclerotherapy (EIS) is one of the major endoscopic approaches for treating esophageal variceal bleeding. However, complications may occur after EIS, which mainly include retrosternal discomfort/pain, dysphagia, re-bleeding, esophageal ulcer, esophageal strictures, and esophageal perforation, etc. In this article, we reported a 36-year-old male who developed esophageal ulcer related bleeding after EIS. Currently, there is no consensus on the treatment strategy for esophageal ulcer-related bleeding after EIS. In the present case, the following treatment strategy may be effective for ulcer related bleeding. The first step is to inhibit gastric acid secretion and reduce portal pressure by intravenous infusion of esomeprazole and somatostatin, respectively. The second is local hemostasis by oral norepinephrine and lyophilizing thrombin powder. The third is to protect digestive tract mucosa by oral Kangfuxin Ye and aluminum phosphate.

Superior Glycemic Control With a Glucose-Responsive Insulin Analog: Hepatic and Nonhepatic Impacts.

We evaluated the hepatic and nonhepatic responses to glucose-responsive insulin (GRI). Eight dogs received GRI or regular human insulin (HI) in random order. A primed, continuous intravenous infusion of [3-3H]glucose began at -120 min. Basal sampling (-30 to 0 min) was followed by two study periods (150 min each), clamp period 1 (P1) and clamp period 2 (P2). At 0 min, somatostatin and GRI (36 ± 3 pmol/kg/min) or HI (1.8 pmol/kg/min) were infused intravenously; basal glucagon was replaced intraportally. Glucose was infused intravenously to clamp plasma glucose at 80 mg/dL (P1) and 240 mg/dL (P2). Whole-body insulin clearance and insulin concentrations were not different in P1 versus P2 with HI, but whole-body insulin clearance was 23% higher and arterial insulin 16% lower in P1 versus P2 with GRI. Net hepatic glucose output was similar between treatments in P1. In P2, both treatments induced net hepatic glucose uptake (HGU) (HI mean ± SEM 2.1 ± 0.5 vs. 3.3 ± 0.4 GRI mg/kg/min). Nonhepatic glucose uptake in P1 and P2, respectively, differed between treatments (2.6 ± 0.3 and 7.4 ± 0.6 mg/kg/min with HI vs. 2.0 ± 0.2 and 8.1 ± 0.8 mg/kg/min with GRI). Thus, glycemia affected GRI but not HI clearance, with resultant differential effects on HGU and nonHGU. GRI holds promise for decreasing hypoglycemia risk while enhancing glucose uptake under hyperglycemic conditions.

Management of Well-differentiated Gastroenteropancreatic Neuroendocrine Tumors (GEPNETs): A Review.

PURPOSE: Neuroendocrine tumors (NETs) are heterogeneous tumors that arise from the neuroendocrine cells of the digestive tract and other organs, such as the lung, ovary, and thyroid glands. They can be well differentiated or poorly differentiated, and management of these tumors differs for each histologic subtype. We have performed a review of NETs and focused on management of well-differentiated gastroenteropancreatic neuroendocrine tumors (GEPNETs) and carcinoid syndrome. METHODS: A PubMed search was performed to obtain articles on the management of well-differentiated NETs. Using the key words neuroendocrine tumors, carcinoid, pNET, octreotide, somatostatin analogues, and radiolabeled therapy, we reviewed Phase II and III trials that were published over the past 30 years. We also reviewed guidelines from the European Neuroendocrine Tumor Society, North America Neuroendocrine Tumor Society, and National Comprehensive Cancer Network in our search. FINDINGS: NETs are usually slow-growing tumors that remain asymptomatic for a long duration and can be either nonfunctioning or functioning. Surgical resection is recommended for locoregional disease, impending obstruction, symptom control, and advanced disease. Nonsurgical treatment options include somatostatin analogues (SSAs), multikinase inhibitors, targeted therapy, chemotherapy, and radiolabeled SSAs. Carcinoid syndrome is mainly treated with SSAs. IMPLICATIONS: Although GEPNETs are slow-growing tumors, most patients are diagnosed with metastatic disease, and therefore it is important that the management of each patient be discussed in a multidisciplinary setting to optimize the treatment strategy. Patients should be considered for clinical trials and refractory cases referred to a specialty center.

The effect of somatostatin retained enema in the treatment of pancreatic ileus.

OBJECTIVE: To analyze the therapeutic effects of somatostatin retained enema in the treatment of pancreatic ileus in the clinic. PATIENTS AND METHODS: 79 patients randomly divided into 41 cases in the observation group and 38 cases in the control group were analyzed. The control group applied basic treatment plan. The observational group applied the same treatment combined with somatostatin retained enema, conducted twice every day and at least 30 minutes every time. Every 7 days' treatment made a course. The clinical therapeutic effects were compared. RESULTS: The levels of the hemo diastase and urinary amylase in both groups were decreased prominently after treatment. The levels of blood calcium were prominently increased (p<0.05) with even more improvement in the observation group (p<0.05). The relief times of the abdominal ache and distention, the recovery time of bowel sound and the first defecation time in the observation group were shorter (p<0.05) than those in the control group. The levels of blood serum IL-6 and TNF-α in the two groups were prominently decreased (p<0.05) after treatment, with even more obvious improvement in the observation group. The therapeutic effective rate of the observational group was prominently higher (p<0.05) than that in the control group. The occurrence rate of the complications was lower. CONCLUSIONS: The application of somatostatin retained enema in the treatment of pancreatic ileus is preferably safe and effective, and it deserves clinical promotion and application.

Systematic review: pharmacotherapy for high-output enterostomies or enteral fistulas.

BACKGROUND: High-output enterocutaneous fistula or enterostomies can cause intestinal failure. There is a wide variety of options in medical management of patients with high output. AIM: To systematically review the literature on available pharmacotherapy to reduce output and to propose an algorithm for standard of care. METHODS: Relevant databases were systematically reviewed to identify studies on pharmacotherapy for reduction in (high-) output enterostomies or fistula. Randomised controlled trials and within subjects controlled prospective trials were included. An algorithm for standard of care was generated based on the outcomes of the systematic review. RESULTS: Two studies on proton pump inhibitors, six on anti-motility agents, three on histamine receptor antagonists, one on an α2- receptor agonist and eight on somatostatin (analogues) were included. One study examined a proton pump inhibitor and a histamine receptor antagonist within the same patients. Overall, we found evidence for the following medical therapies to be effective: omeprazole, loperamide and codeine, ranitidine and cimetidine. On the basis of these outcomes and clinical experience, we proposed an algorithm for standard of care which consists of high-dose proton pump inhibitors combined with high-dose loperamide as the first step followed by addition of codeine in case of insufficient output reduction. So far, there is insufficient evidence for the standard use of somatostatin (analogues). CONCLUSIONS: The available evidence on the efficacy of medication to reduce enterostomy or enterocutaneous fistula output is hampered by low quality studies. We propose an algorithm for standard of care output reduction in these patients.

Congenital fibrosarcoma in complete remission with Somatostatin, Bromocriptine, Retinoids, Vitamin D3, Vitamin E, Vitamin C, Melatonin, Calcium, Chondroitin sulfate associated with low doses of Cyclophosphamide in a 14-year Follow up.

At birth, a male child presented a 6 cm tumour in the right leg. The tumour was partially removed after just 12 days. Histology showed a congenital fibrosarcoma associated with reactive lymphadenitis. A first cycle of adjuvant chemotherapy did not prevent the rapid progression of the disease. Subsequent evaluation for surgical removal raised serious concerns due to the need for a major operation involving total amputation of the right leg and hemipelvectomy. Since surgery could not exclude the possibility of disease recurrence and since the traditional cycles of chemotherapy did not offer any possibility of a cure, the parents opted for the Di Bella Method. The combined use of Somatostatin, Melatonin, Retinoids solubilized in Vit. E, Vit. C, Vit. D3, Calcium, and Chondroitin sulfate associated with low doses of Cyclophosphamide resulted in a complete objective response, still present 14 years later, with no toxicity and without the need for hospitalization, allowing a normal quality of life and perfectly normal adolescent psycho-physical development.

GEP-NETs update: Biotherapy for neuroendocrine tumours.

Neuroendocrine tumours (NETs) represent a less frequent and heterogeneous group of tumours, which has experienced, in recent years, a significant increase in effective therapeutic possibilities overcoming the disappointing results from chemotherapy. Initial improvements in treatment strategies came from somatostatin analogues (SSAs) that have widely demonstrated a significant improvement in symptomatic relief and tumour control growth by a complex mechanism of action over cell survival, angiogenesis and immunomodulation. Recent investigations have pointed out novel SSAs with a wider binding profile (pasireotide), chimeric molecules against somatostatin receptors and dopamine receptors and the combination with targeted agents, such as mTOR inhibitors or antiangiogenic agents. Immunotherapy is the second cornerstone in NET treatment and has been represented with interferon alpha for a long time, with a demonstrated activity on tumour and clinical response. Its less manageable adverse events have limited its usage. However, different checkpoints in immune system regulation have been effectively targeted in different solid tumours, and novel approaches are currently arising in NETs. In conclusion, biotherapy remains an active treatment strategy for initial approach in patients with NETs. Further investigation on patients' selection, molecular profiles, treatment sequence or combination and optimisation of current and novel biotherapy agents is required.

Selective agonists of somatostatin receptor subtype 1 or 2 injected peripherally induce antihyperalgesic effect in two models of visceral hypersensitivity in mice.

Somatostatin interacts with five G-protein-coupled receptor (sst1-5). Octreotide, a stable sst2≫3≥5 agonist, exerts a visceral anti-hyperalgesic effect in experimental and clinical studies. Little is known on the receptor subtypes involved. We investigated the influence of the stable sst1-5 agonist, ODT8-SST and selective receptor subtype peptide agonists (3 or 10µg/mouse) injected intraperitoneally (ip) on visceral hypersensitivity in mice induced by repeated noxious colorectal distensions (four sets of three CRD, each at 55mmHg) or corticotropin-releasing factor receptor 1 agonist, cortagine given between two sets of graded CRD (15, 30, 45, and 60mmHg, three times each pressure). The mean visceromotor response (VMR) was assessed using a non-invasive manometry method and values were expressed as percentage of the VMR to the 1st set of CRD baseline or to the 60mmHg CRD, respectively. ODT8-SST (10µg) and the sst2 agonist, S-346-011 (3 and 10µg) prevented mechanically induced visceral hypersensitivity in the three sets of CRD, the sst1 agonist (10µg) blocked only the 2nd set and showed a trend at 3µg while the sst4 agonist had no effect. The selective sst2 antagonist, S-406-028 blocked the sst2 agonist but not the sst1 agonist effect. The sst1 agonist (3 and 10µg) prevented cortagine-induced hypersensitivity to CRD at each pressure while the sst2 agonist at 10µg reduced it. These data indicate that in addition to sst2, the sst1 agonist may provide a novel promising target to alleviate visceral hypersensitivity induced by mechanoreceptor sensitization and more prominently, stress-related visceral nociceptive sensitization.

Estradiol regulates GH-releasing peptide's interactions with GH-releasing hormone and somatostatin in postmenopausal women.

OBJECTIVE: Estrogen stimulates pulsatile secretion of GH, via mechanisms that are largely unknown. An untested hypothesis is that estradiol (E2) drives GH secretion by amplifying interactions among GH-releasing hormone (GHRH), somatostatin (SS), and GH-releasing peptide (GHRP). DESIGN: The design comprised double-blind randomized prospective administration of transdermal E2 vs placebo to healthy postmenopausal women (n=24) followed by pulsatile GHRH or SS infusions for 13 h overnight with or without continuous GHRP2 stimulation. METHODS: End points were mean concentrations, deconvolved secretion, and approximate entropy (ApEn; a regularity measure) of GH. RESULTS: By generalized ANOVA models, it was observed that E2 vs placebo supplementation: i) augmented mean (13-h) GH concentrations (P=0.023), GHRH-induced pulsatile GH secretion over the first 3 h (P=0.0085) and pulsatile GH secretion over the next 10 h (P=0.054); ii) increased GHRP-modulated (P=0.022) and SS-modulated (P<0.001) GH ApEn; and iii) did not amplify GHRH/GHRP synergy during pulsatile GH secretion. By linear regression, E2 concentrations were found to be positively correlated with GH secretion during GHRP2 infusion (P=0.022), whereas BMI was found to be negatively correlated with GH secretion during GHRH (P=0.006) and combined GHRH/GHRP (P=0.015) stimulation. E2 and BMI jointly determined triple (combined l-arginine, GHRH, and GHRP2) stimulation of GH secretion after saline (R²=0.44 and P=0.003) and pulsatile GHRH (R²=0.39 and P=0.013) infusions. CONCLUSION: In summary, in postmenopausal women, E2 supplementation augments the amount (mass) and alters the pattern (regularity) of GH secretion via interactions among GHRH, SS, GHRP, and BMI. These outcomes introduce a more complex model of E2 supplementation in coordinating GH secretion in aging women.

Evaluation of the safety and efficacy of the first-line treatment with somatostatin combined with melatonin, retinoids, vitamin D3, and low doses of cyclophosphamide in 20 cases of breast cancer: a preliminary report.

OBJECTIVE: The current strategies for the treatment of breast cancer are essentially based on surgery, preceded and/or followed by chemotherapy often supplemented by radiotherapy and/or the administration of hormonal therapy and monoclonal antibodies. Their combined use has made it possible to increase an overall survival but they are still penalized by adverse effects and toxicity. The marked anti-cancer effects of biological molecule such as somatostatin, melatonin, retinoid, vitamin D3 and prolactin inhibitors have been studied and documented for several decades. Their integrated and synergic action have been demonstrated, but only a few studies have as yet been carried out on their combined application in humans. The aim of the present investigation was to evaluate both the objective clinical response and toxicity of the biological multimodal treatment named Di Bella Method (DBM). MATERIAL AND METHODS: The clinical data from a total of 20 women with a certified diagnosis of breast cancer,defined disease stage, and who independently decided to follow the DBM as first-line treatment, were retrospectively reviewed. RESULTS: The mean age of the patients was 51 years (min 30; max 73). Twelve (12) patients (60%) presented an early stage disease, while the other 40% had a locally advanced/metastatic stage. An overall clinical benefit was achieved in 75% of cases, with 55% of complete response and 20% of partial response. For metastatic patients, the overall survival rate was 71%. The main toxicity effects included leukopenia, gastrointestinal phenomena and drowsiness. CONCLUSIONS: The preliminary results of this report confirm the positive action of the biological treatment in terms of efficacy and survival, showing a more than favorable profile of tolerability.

Synthesis and evaluation of biodegradable PCL/PEG nanoparticles for neuroendocrine tumor targeted delivery of somatostatin analog.

PURPOSE: Neuroendocrine tumors often present a diagnostic and therapeutic challenge. We have aimed to synthesize and develop biodegradable nanoparticles of somatostatin analogue, octreotide for targeted therapy of human neuroendocrine pancreatic tumor. METHODS: Direct solid phase peptide synthesis of octreotide was done. Octreotide loaded PCL/PEG nanoparticles were prepared by solvent evaporation method and characterized for transmission electron microscopy, differential scanning calorimetery (DSC), Zeta potential measurement studies. The nanoparticles were evaluated in vitro for release studies and peptide content. For biological evaluations, receptor binding & cytotoxicity studies were done on BON-1 neuroendocrine tumor cell line. Biodistribution of radiolabeled peptide and nanoparticles, tumor regression studies were performed on tumor-bearing mouse models. RESULTS: We have synthesized and purified octreotide with the purity of 99.96% in our laboratory. PEG/PCL nanoparticles with an average diameter of 130-195 nm having peptide loading efficiency of 66-84% with a negative surface charge were obtained with the formulation procedure. Octreotide nanoparticles have a negative action on the proliferation of BON-1 cells. In vivo biodistribution studies exhibited major accumulation of octreotide nanoparticles in tumor as compared to plain octreotide. Octreotide nanoparticles inhibited tumor growth more efficiently than free octreotide. CONCLUSIONS: Thus, it was concluded that the PCL/PEG nanoformulation of octreotide showed high tumor uptake due to the enhanced permeation and retention (EPR) effect and then peptide ligand imparts targetability to the sst2 receptor and there by showing increase tumor growth inhibition. Selective entry of nanoparticles to the tumor also give the reduce side effects both in vivo and in vitro.

Erasure of a spinal memory trace of pain by a brief, high-dose opioid administration.

Painful stimuli activate nociceptive C fibers and induce synaptic long-term potentiation (LTP) at their spinal terminals. LTP at C-fiber synapses represents a cellular model for pain amplification (hyperalgesia) and for a memory trace of pain. µ-Opioid receptor agonists exert a powerful but reversible depression at C-fiber synapses that renders the continuous application of low opioid doses the gold standard in pain therapy. We discovered that brief application of a high opioid dose reversed various forms of activity-dependent LTP at C-fiber synapses. Depotentiation involved Ca(2+)-dependent signaling and normalization of the phosphorylation state of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. This also reversed hyperalgesia in behaving animals. Opioids thus not only temporarily dampen pain but may also erase a spinal memory trace of pain.

The Di Bella Method (DBM) improved survival, objective response and performance status in a retrospective observational clinical study on 55 cases of lymphomas.

OBJECTIVES: Lymphomas are the main form of haematological neoplasms, representing 55.6% of all tumours of the blood. Overall, they account for 5.3% of all malignant tumours (excluding basal and squamous cell skin cancer) in Italy with a prevalence constantly increasing at a rate of 3% per year. From a histological point of view, they represent a vast heterogeneous group of haematological diseases, their staging being based on defined cyto-morphological and anatomo-pathological criteria. Although the combined use of standard approaches can provide good response rates, recurrence is particularly frequent in patients undergoing traditional treatment, with critical and often irreversible side effects such as myelosuppression and a high frequency of opportunistic infections and sterility. Numerous epidemiological studies and preclinical data have for some time now reported the anticancer effects of molecules such as Melatonin, Retinoids, Vitamins E, D3, and C, Somatostatin and prolactin inhibitors in neoplastic diseases. There are, however, very few publications on the combined effects of these substances in vivo. METHODS: We report an observational study carried out on 55 patients affected by various forms of lymphoma, treated with the biological therapy known as the Di Bella Method (DBM). The 1, 3 and 5-year survival rates are reported, together with any signs of toxicity. RESULTS: The DBM treatment achieved partial or complete objective responses in a shorter time and in greater percentages if administered as first-line therapy. The adjuvant treatment increased survival time and improved quality of life with respect to the data reported in the literature for the same types and stages of lymphoma. CONCLUSION: Overall, the treatment was well tolerated, with minor and transient side effects. The patients were able to continue the treatment at home, carrying out their normal activities without problems.

From somatostatin to octreotide LAR: evolution of a somatostatin analogue.

BACKGROUND: Acromegaly is characterized by overproduction of growth hormone (GH) by the pituitary gland. GH stimulates the synthesis of insulin-like growth factor-I (IGF-I), and the somatic growth and metabolic dysfunction that characterize acromegaly are a consequence of elevated GH and IGF-I levels. Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare, slow-growing neoplasms that have usually metastasized by the time of diagnosis. The majority of GEP-NETs are carcinoid tumors whose syndrome is caused by the hypersecretion of biogenic amines, peptides and polypeptides responsible for the principal symptoms of diarrhea and flushing. METHODS: The MEDLINE and EMBASE databases were searched for preclinical and clinical studies of octreotide (Sandostatin* ), a potent synthetic somatostatin analogue, in patients with acromegaly or GEP-NETs. OBJECTIVE: This article reviews the 20 years of clinical experience with octreotide and the impact it has made in patients with acromegaly or GEP-NETs. RESULTS: Octreotide has proven to be an essential component in the management strategy of acromegaly and GEP-NETs over the past 20 years. The multiple beneficial effects of octreotide throughout the body, combined with its established safety profile (the most common adverse effects are injection-site pain and gastrointestinal events), have made it an appealing option for clinicians. The advent of the long-acting release (LAR) formulation of octreotide provided additional benefits to patients through monthly administration, while maintaining the efficacy and tolerability profile of the daily subcutaneous formulation. CONCLUSIONS: Octreotide is a potent synthetic somatostatin analogue that has become the mainstay of medical therapy for tumor control in neuroendocrine disorders such as acromegaly and GEP-NETs. The development of octreotide LAR offered a further advancement; less frequent dosing provided valuable benefits in quality of life to patients, with equivalent efficacy and tolerability. Moreover, recent results from the PROMID study have confirmed the antiproliferative effect of octreotide LAR in patients with well-differentiated metastatic GEP-NETs of the midgut. New therapeutic uses of octreotide are currently under investigation in a variety of clinical settings.

Addition of somatostatin-14 to a standard total parenteral nutrition-mixture in the treatment of fistulae: a clinical, double-blind, randomised, cross-over study.

UNLABELLED: BACKGROUND/STUDY AIMS: Somatostatin and total parenteral nutrition (TPN) are routinely used in the treatment of pancreatic and enterocutaneous fistulae. The objective of this clinical randomised cross-over study was to investigate the serum levels of somatostatin infused alongside TPN by a separate intravenous line, and when it had been added to the TPN mixture. PATIENTS/METHODS: The subjects were recruited by the treating physicians and the nutrition nurses. From the patients who started the study, no one dropped out. Ten patients were treated with a standard TPN mixture and somatostatin 6 mg/day. Patients were randomised to two possible regimens: 'somatostatin plus TPN--somatostatin separately--somatostatin plus TPN' or 'somatostatin separately--somatostatin plus TPN--somatostatin separately'. Each regimen consisted of 3 x 3 days of therapy, during which, serum levels of somatostatin were measured daily. Pre- and posttreatment samples were also analysed. RESULTS: When somatostatin was infused separately, the mean serum level was 884.8 pg/ml (SD: 557.3; range: 54-1900). When added to TPN, the mean serum level was 807.5 pg/ml (SD: 505.8; range 162-2279) (p value of difference = 0,473). The mean pretreatment level was 17.1 pg/ml (SD: 7.5; range: 8-33), and posttreatment was 32.8 pg/ml (SD: 26.5; range: 16-97). CONCLUSIONS: These results demonstrate that serum levels of somatostatin are similar in both treatment regimens and therefore may be added to a TPN mixture.

Neuroendocrine tumors. Biotherapy.

This review gives an introduction to the classification and staging of neuroendocrine tumors, as the prognostic implications of these classifications influence therapeutic decisions. The indications for biotherapy are given, together with a short update on the mechanism of somatostatin analogs and interferon-alpha therapy. This is followed by an in-depth description of the use of biotherapy, its results with respect to symptomatic and antiproliferative treatment, as well as its side-effects.

Comparison of integrated Chinese and Western medicine with and without somatostatin supplement in the treatment of severe acute pancreatitis.

AIM: To evaluate the therapeutic effect of the combined use of early short-term somatostatin and conventional integrated Chinese and Western medicine in treating severe acute pancreatitis. METHODS: Sixty patients with severe acute pancreatitis were divided at random into a somatostatin group and a basic treatment group. Both groups received integrated traditional Chinese and Western medicine without surgery. For patients in the somatostatin group, somatostatin was infused intravenously 250 microg/h for 72 h; other medications were the same as in the basic treatment group. In both groups, comparisons of therapeutic effectiveness were made in terms of morbidity of organic dysfunction and mortality rate, and severity of the disease according to serum levels of C-reaction protein, scores of acute physiology and chronic health evaluation (APACHE II), and scores of Balthazar-CT. RESULTS: The indexes for C-reaction protein levels on the fourth and seventh days, and APACHE II scores on the seventh day after treatment, were significantly improved in the somatostatin group than in the basic treatment group. The morbidity of organic dysfunction was lower in the somatostatin group than in the basic treatment group, although the difference was not statistically significant. There was no significant difference in mortality between the two groups. CONCLUSION: We conclude that combined traditional Chinese and Western medicines with an early short-term use of somatostatin can improve the condition of patients with severe acute pancreatitis.

Regulation by estradiol of hypothalamic somatostatin gene expression: possible involvement of somatostatin in the control of luteinizing hormone secretion in the ewe.

In the ewe, the mediobasal hypothalamus (MBH) is the primary central site for estradiol to generate the preovulatory GnRH/LH surges and sexual behavior. This area contains numerous neurons expressing the estradiol receptor alpha, distributed in the ventromedial nucleus (VMN) and the infundibular nucleus (IN). A large proportion of these neurons express somatostatin, making this neuropeptide a potential candidate for transmission of the estradiol signal to the GnRH neurons located in the preoptic area. We tested this hypothesis using ovariectomized ewes that had been subjected to an artificial estrous cycle. In the first experiment, 22 h after progesterone removal, ewes received estradiol (treated ewes) or empty implants (control ewes) for 4 h and then were killed. Using in situ hybridization, we showed that this short estradiol treatment increased the somatostatin mRNA amount by about 50% in the VMN and 42% in the IN. In the second experiment, preovulatory estradiol signal was replaced by somatostatin intracerebroventricular (ICV) administration. This treatment abolished LH pulsatility and dramatically decreased the mean basal level of LH secretion while it did not affect the mean plasma GH concentration. We demonstrated that an increase in somatostatin mRNA occurs at the time of the negative feedback effect of estradiol on LH secretion during the early stage of the GnRH surge induction. As ICV somatostatin administration inhibits the pulsatile LH secretion by acting on the central nervous system, we suggest that somatostatin synthesized in the MBH could be involved in the estradiol negative feedback before the onset of the preovulatory surge.

Photic stimulation inhibits growth hormone secretion in rats: a hypothalamic mechanism for transient entrainment.

It is well established that photic cues are used by the suprachiasmatic nucleus (SCN) to entrain circadian rhythms to the light/dark cycle, but the role of photic stimuli in the regulation of ultradian neuroendocrine rhythms is ill defined. In relation to the rhythms of GH secretion, recent studies have shown that nocturnal photic stimulation induces gene expression not only in the SCN but also in periventricular (PeN) somatostatin (SRIF) neurons. We have, therefore, investigated the effect of nocturnal photic stimulation on spontaneous and induced GH secretion in conscious rats. Nocturnal photic stimulation (lights on at 2400 h for 1 h) suppressed spontaneous GH secretion in male and female rats and reduced the GH response to SRIF withdrawal and iv injection of GH-releasing factor. A similar trough in GH secretion was also observed during the first hour of the normal light phase (0600 h). Using immunohistochemical analysis, we have also shown that expression of the transcription factor, Egr-1, is induced at the commencement of the light phase in the SCN, PeN, and medial preoptic nucleus. This effect is abolished by maintaining rats in the dark during this period. These data, together with our previous demonstration that 50% of SRIF-positive neurons in the PeN coexpress Egr-1 after photic stimulation, suggest that activation of SRIF neurons in the PeN may entrain the episodes of GH secretion to the dark/light interface. However, the absence of synchrony in GH pulses between animals by the second half of the light period suggests that this entrainment is transient.