Andrew Luckey

Corticotropin-releasing factor receptor 1-deficient mice do not develop postoperative gastric ileus.

BACKGROUND & AIMS Corticotropin-releasing factor (CRF) signaling pathways play a key role in the stress response through the activation of CRF(1) and CRF(2) receptors. We investigated the CRF receptor subtypes involved in gastric postoperative ileus. METHODS Adult male mice (C57BL/6, CRF(1)-deficient, and wild-type), fasted for 16-18 hours, were anesthetized for 10 minutes and had a midline celiotomy and cecal exteriorization and palpation for 30 or 60 seconds or no surgery (sham). Phenol red was given by gavage 100 minutes after anesthesia; 20 minutes later, gastric emptying and blood glucose level were measured. RESULTS In C57BL/6 mice, cecal palpation for 30 or 60 seconds significantly reduced gastric emptying to 30.3% +/- 1.4% and 5.8% +/- 3.4%, respectively, compared with 58.5% +/- 4.4% in sham. The CRF(1) antagonist CP-154,526 (20 mg/kg subcutaneously) completely prevented the 30-second cecal palpation-induced delayed gastric emptying (53.0% +/- 7.9% vs. 28.0% +/- 4.0% in vehicle + surgery), whereas the CRF(2) antagonist astressin(2)-B injected subcutaneously had no effect. In CRF(1)-deficient mice, cecal palpation for 30 seconds did not delay gastric emptying (80.3% +/- 4.5% compared with 84.7% +/- 6.3% in sham); in wild-type mice, gastric emptying was decreased to 17.8% +/- 16.1% (P < 0.05 vs. sham 72.0% +/- 12.4%). Surgery increased glucose levels by 46% compared with sham in wild-type mice, while glycemia was not altered in CRF(1)-deficient mice. Basal emptying was similar in wild-type and CRF(1)-deficient mice and not influenced by CRF antagonists in C57BL/6 mice. CONCLUSIONS These data show that CRF(1) activation plays an important role in mediating the early phase of gastric ileus.

Cold ambient temperature reverses abdominal surgery-induced delayed gastric emptying and decreased plasma ghrelin levels in rats

We investigated whether acute cold-induced vagal activation through brainstem thyrotropin-releasing hormone (TRH) signaling influences abdominal surgery-induced delayed gastric emptying (GE) in fasted rats. Laparotomy and cecal palpation or sham (short anesthesia alone) was performed 10 min before or 30 min after cold exposure (4-6°C) lasting 90 min. Non-nutrient GE was assessed during 70-90 min of cold exposure. Control groups remained at room temperature (RT). The stable TRH analog, RX-77368 (50 ng/rat) was injected intracisternally immediately before surgery and GE monitored 30-50 min postsurgery in rats maintained at RT. Plasma acyl (AG) and total ghrelin levels were assessed using the new RAPID blood processing method and radioimmunoassays. Desacyl ghrelin (DAG) was derived from total minus AG. In rats maintained at RT, abdominal surgery decreased GE by 60% compared to sham. Cold before or after surgery or RX-77368 normalized the delayed GE. In non-fasted rats, cold exposure increased plasma AG and DAG levels at 2 h (2.4- and 2.7-times, respectively) and 4 h (2.2- and 2.0-times, respectively) compared to values in rats maintained at RT. In fasted rats, abdominal surgery decreased AG and DAG levels by 2.4- and 2.1-times, respectively, at 90 min. Cold for 90 min after surgery normalized AG and DAG levels to those observed in sham-treated animals kept at RT. These data indicate that endogenous (cold exposure) and exogenous (TRH analog) activation of medullary TRH vagal signaling prevent abdominal surgery-induced delayed GE. The restoration of circulating AG levels inhibited by abdominal surgery may contribute to alleviate postoperative gastric ileus.

Central administration of pan-somatostatin agonist ODT8-SST prevents abdominal surgery-induced inhibition of circulating ghrelin, food intake and gastric emptying in rats.

Background  Activation of brain somatostatin receptors (sst1–5) with the stable pan‐sst1–5 somatostatin agonist, ODT8‐SST blocks acute stress and central corticotropin‐releasing factor (CRF)‐mediated activation of endocrine and adrenal sympathetic responses. Brain CRF signaling is involved in delaying gastric emptying (GE) immediately post surgery. We investigated whether activation of brain sst signaling pathways modulates surgical stress‐induced inhibition of gastric emptying and food intake.

The Newly Developed CRF1-Receptor Antagonists, NGD 98-2 and NGD 9002, Suppress Acute Stress-Induced Stimulation of Colonic Motor Function and Visceral Hypersensitivity in Rats

Corticotropin releasing factor receptor 1 (CRF1) is the key receptor that mediates stress-related body responses. However to date there are no CRF1 antagonists that have shown clinical efficacy in stress-related diseases. We investigated the inhibitory effects of a new generation, topology 2 selective CRF1 antagonists, NGD 98-2 and NGD 9002 on exogenous and endogenous CRF-induced stimulation of colonic function and visceral hypersensitivity to colorectal distension (CRD) in conscious rats. CRF1 antagonists or vehicle were administered orogastrically (og) or subcutaneously (sc) before either intracerebroventricular (icv) or intraperitoneal (ip) injection of CRF (10 µg/kg), exposure to water avoidance stress (WAS, 60 min) or repeated CRD (60 mmHg twice, 10 min on/off at a 30 min interval). Fecal pellet output (FPO), diarrhea and visceromotor responses were monitored. In vehicle (og)-pretreated rats, icv CRF stimulated FPO and induced diarrhea in >50% of rats. NGD 98-2 or NGD 9002 (3, 10 and 30 mg/kg, og) reduced the CRF-induced FPO response with an inhibitory IC50 of 15.7 and 4.3 mg/kg respectively. At the highest dose, og NGD 98-2 or NGD 9002 blocked icv CRF-induced FPO by 67–87% and decreased WAS-induced-FPO by 23–53%. When administered sc, NGD 98-2 or NGD 9002 (30 mg/kg) inhibited icv and ip CRF-induced-FPO. The antagonists also prevented the development of nociceptive hyper-responsivity to repeated CRD. These data demonstrate that topology 2 CRF1 antagonists, NGD 98-2 and NGD 9002, administered orally, prevented icv CRF-induced colonic secretomotor stimulation, reduced acute WAS-induced defecation and blocked the induction of visceral sensitization to repeated CRD.

Central Action of Pan-Somatostatin Agonist ODT-8 to Prevent Abdominal Surgery-Induced Reduction of Circulating Acyl Ghrelin, Gastric Emptying and Food Intake

the effect of CCK and leptin interaction on intragastric pressure, suggesting CCK acts on low affinity CCKAR to enhance leptin action on gastric motility. CART is present in the nodose ganglia (NG). Immunostaining of NG obtained from fasting rats showed little or no CART immunoreactivities. A marked increase in CART staining in 19+3% of NG neurons was observed 30” following CCK8 (0.5 μg/kg) administration. 95+3% of this group of neurons contained both CCKAR and leptin receptor. The inhibitory action of leptin/CCK on gastric motility was abolished by electroporation of the NG with CART siRNA. We have previously demonstrated that the synergistic interaction between leptin and CCK in the NG involves cross talk between CCK/SRC cascades and the leptin/JAK/PI3K/STAT3. We showed that electroporation of the NG with siRNA of SRC or PI3 kinase or STAT3 but not MAPK reduced >80% of the inhibitory action of leptin/CCK on gastric motility. We conclude that CCK potentiates leptins ability to evoke gastric relaxation. This is mediated by NG release of CART which acts via the vago-vagal pathway to evoke gastric relaxation. Leptin interacts with CCK via a CCK/SRC cascade and leptin/PI3K/STAT3 signaling pathway to stimulate increased CART transcription and its release. Hence acting in concert with CCK, leptin not only is an important mediator of satiety but also regulates the entry of nutrients into the intestine through its action on gastric motility.