Peripheral corticotropin releasing hormone mediates post-inflammatory visceral hypersensitivity in rats

AIM:To investigate whether peripheral corticotropin releasing hormone (CRH), which is up-regulated in intestinal inflammation, mediates the post-inflammatory visceral hypersensitivity in a rat model of colitis. METHODS:We measured mucosal myeloperoxidase (MPO) activity as a marker of inflammation, plasma CRH level, and abdominal withdrawal reflex (AWR) to colorectal distension as a visceral nociceptive response at 2, 7 and 14 d after the induction of colitis with 4% acetic acid. RESULTS:Colonic inflammation, quantified by MPO activity, significantly increased on d 2 and subsided thereafter, which indicated a resolution of inflammation within 7 d. On the contrary, plasma CRH level and AWR score were increased on d 2, remained high on d 7, and returned to control level on d 14. Intraperitoneal injection of a CRH antagonist, astressin (30 μg/kg), significantly attenuated the post-inflammatory visceral hypersensitivity on d 7. Furthermore, intraperitoneal administration of CRH (3 and 10 μg/kg) mimicked the post-inflammatory visceral hypersensitivity in naive rats. CONCLUSION:These results suggest that increased peripheral CRH mediates the enhanced visceral nociception in rats recovered from experimental colitis.

Effects of high dose glucocorticoid on expression and mRNA transcription of corticotropin releasing hormone in hypothalamus paraventricular nucleus of rats

Objective： To explore the effect of high dose of glucocorticoid （GC） on the synthesis of corticotropin releasing hormone （CRH） and transcription of its mRNA in hypothalamus paraventricular nuclei （PVN） in order to investigate its difference with that of traditional GC effects and to add a new possible explanation to the mechanism of clinical applications of high dose of GC. Methods： A total of 60 rats were divided into 5 groups： blank control, 10^-6 mol/L dexamethasone （DEX） group, 10^-9 mol/L DEX group, 0.9% saline group and GR blocking group （10^-2mol/L RU486）. All agents were administrated through the femoral vein. CRH protein expression was measured by immunohistochemistry and laser confocal scanning microscopy （LCSM）; CRH mRNA level was explored by in situ hybridization. Results： 10^-6 mol/L DEX made CRH mRNA transcripted after 20 min and its protein expressed in PVN after 30 min, while normal level of DEX and 0.9% saline could not. If GR was blocked in advance, the effect of high dose of DEX disappeared. Conclusion ： High dose of GC can have CRH increased in PVN, which differs to the effect of traditional GC. And mGRH may play an important role in the effect of high dose of GC but not classic iGR.

Effects of injection of anti-corticotropin release hormone serum in the lateral ventricles and electroacupuncture analgesia on pain threshold in rats with adjuvant arthritis

Rat models of adjuvant arthritis were established, and anti-corticotropin release hormone serum injection in the lateral ventricles and electroacupuncture at right Jiaji （EX-B2） were performed. The pain threshold was decreased at 45 and 60 minutes after injection of the anti-corticotropin release hormone serum. Electroacupuncture at Jiaji can resist this effect. Immunohistochemical staining results showed that the expression of corticotropin release hormone in the hypothalamic paraventdcular nucleus was greater in the electroacupuncture ＋ anti-corticotropin release hormone serum group compared with the anti-corticotropin release hormone serum group. The expression of corticotropin release hormone was correlated with the pain threshold. The effect of endogenous corticotropin release hormone in pain modulation can be obstructed by anti-corticotropin release hormone serum. The analgesia of electroacupuncture can partially resist the depressed pain threshold caused by injection of anti-corticotropin release hormone serum. The analgesic effect of electroacupuncture is associated with the corticotropin release hormone content in the hypothalamus.

The cAMP-mediated protein kinase signal transduction pathway is involved in the pyrogenic effect of CRH in rats

To determine whether the cyclic adenosine monophosphate (cAMP) mediated protein kinase signal transduction pathway is involved in the pyrogenic action of corticotropin releasing hormone (CRH) in rats.Methods Corticotropin releasing hormone, 2', 3 '-dideoxyadenosine (DDA) and adenosine-3', 5'(cyclic) monophosphorothionate, Rp-lsomer (Rp-cAMPS), were administered intracerebroventricularly (i.c.v.). The colonic temperature was measured using a thermistor, and the content of cAMP in the hypothalamus was determined by radioimmunoassay. Hypethalemic incubation was used to assess the effects of CRH on the content of cAMP in the hypothalamus in vitro.Results Microinjection (i.c.v.) of CRH (2.5 μg, 5.0 μg and 10 μg) caused increases in colonic temperature and the hypothalemus cAMP level in conscious rats. CRH increased hypothalemus cAMP level in vitro. The pyrogenic effects of CRH were abolished or markedly inhibited by prior injection (i. c. v. ) of an adenylate cyclase inhibitor, DDA (30 μg), or an inhibitor of cAMP-dependent protein kinase, Rp-cAMPS (15 μg).Conclusion cAMP mediates the pyrogenic action of centrally administered of CRH in rats, and protein kinase A may play an important role in the central CRH-induced fever. The cAMP-dependent protein kinase signal transduction pathway may be involved in the central mechanisms of the pyrogenic action of CRH in rats.

Altered Neuronal Activity in the Central Nucleus of the Amygdala Induced by Restraint Water-Immersion Stress in Rats

Restraint water-immersion stress(RWIS), a compound stress model, has been widely used to induce acute gastric ulceration in rats. A wealth of evidence suggests that the central nucleus of the amygdala(CEA) is a focal region for mediating the biological response to stress. Different stressors induce distinct alterations of neuronal activity in the CEA; however, few studies have reported the characteristics of CEA neuronal activity induced by RWIS. Therefore, we explored this issue using immunohistochemistry and in vivo extracellular single-unit recording. Our results showed that RWIS and restraint stress(RS) differentially changed the c-Fos expression and firing properties of neurons in the medial CEA. In addition,RWIS, but not RS, induced the activation of corticotropinreleasing hormone neurons in the CEA. These findings suggested that specific neuronal activation in the CEA is involved in the formation of RWIS-induced gastric ulcers.This study also provides a possible theoretical explanation for the different gastric dysfunctions induced by different stressors.

Social dominance-related major urinary proteins and the regulatory mechanism in mice

Major urinary proteins(MUPs)have been proven to be non-volatile male pheromones in mice.Here,we aimed to elucidate the relationship between MUPs and dominance hierarchy,and the underlying molecular mechanisms.Dominance–submission relationship was established by chronic dyadic encountering.We found that at the urinary protein level and hepatic mRNA level,the expression of major MUPs,including Mup20,was enhanced in dominant males compared with subordinate males,indicating that MUPs might signal the social status of male mice.Meanwhile,the mRNA level of hepatic corticotropin releasing hormone receptor 2(CRHR2)was higher in subordinate male mice than in dominant male mice.Castration also enhanced the expression of CRHR2,but suppressed that of MUPs.CRHR2 agonist treatment reduced the expression of MUPs in liver.However,male social status failed to exert significant influence on serum testosterone and corticosterone as well as the mRNA expression of their receptors.These findings reveal that some MUPs,especially Mup20,might constitute potential dominance pheromones and could be downregulated by hepatic CRHR2,which is possibly independent of androgen or corticosterone systems.