Role of the 5-HT receptor in neurogenic inflammation in Fisher 344 rat airways

The increased plasma protein extravasation in the airways of Fisher 344 rats upon stimulation of sensory nerves is in part due to the degranulation of mast cells. In this study, we examined the role of 5-HT and histamine receptors in the capsaicin-induced increase in plasma protein extravasation in Fisher 344 rat airways, using Evans blue as an intravascular marker. We found that only 5-HT2 receptor agonists increased baseline plasma protein extravasation. Furthermore, the 5-HT2 receptor antagonist ketanserin reduced the capsaicin-induced increase in plasma protein extravasation. Combining ketanserin with the tachykinin NK1 receptor antagonist (+/-)-RP 67,580 ((3alphaR,7alphaR)-(7,7-diphenyl-2(1-imino-2-(2-methoxyph enylethyl)-perhydraisoinositol-4-one))) abolished the neurogenic increase in plasma protein extravasation. Finally, using selective receptor agonists and antagonists, we demonstrated that there was no modulation of the capsaicin-induced rise in plasma protein extravasation by stimulation of either histamine receptors or 5-HT1, 5-HT3 and 5-HT4 receptors. We conclude that, in the airways of Fisher 344 rats, the neurogenic increase in plasma protein extravasation is caused by activation of both tachykinin NK1 receptors and 5-HT2 receptors.     

Age-related changes in the lipid metabolism of Fisher 344 rats

Lipid metabolism of male Fisher 344 rats aged 2-24 months was studied. Serum and liver cholesterol levels did not display the age-related gradual increase seen in other rat strains. An increase in the serum plus liver cholesterol pool from 2 to 6 months was followed by a plateau through 18 months and then another increase at 24 months of age. The triglyceride pool increased from 2 to 6 months and then remained unchanged through 24 months of age. Cholesterol synthesis from acetate decreased 50% between 2 and 9 months and fell only slightly through 24 months of age. Assay of 3-hydroxy-3-methyl glutaryl Coenzyme A (HMG-CoA) reductase showed a similar pattern but did not decrease further after 9 months of age. Cholesterol 7alpha hydroxylase activity was not significantly altered by age. These age- and strain-related differences present an opportunity for a comparative study of the aging process using the parameters of lipid metabolism as indicators.     

Increased striatal proenkephalin mRNA subsequent to production of spreading depression in rat cerebral cortex: activation of corticostriatal pathways?

Cortical Spreading Depression (CSD) is a slowly propagating wave of depolarization and negative interstitial DC potential, that when induced in the rat brain extends across the entire homolateral hemisphere. Despite evidence that CSD does not penetrate into subcortical regions, neurochemical changes in areas anatomically connected to cortex have been reported. In this study in situ hybridization histochemistry was used to examine the levels of cholecystokinin (CCK), proenkephalin (ENK) and prodynorphin (DYN) mRNA in cortex and forebrain basal ganglia following KCl-induced CSD. Unilateral CSD was induced by topical application of 3 M KCl ( approximately 10 microliter) onto the right parietal cortex for 10 min and rats were then killed 1-6 h and 1-28 days later. CCK mRNA levels were increased (P<0.01) in the ipsilateral neocortex 3 h after CSD (13% above levels in contralateral side), reached a peak at 2 days ( approximately 70%) and were still elevated at 7 (30%) but not, 14 or 28 days later. Unilateral CSD also produced a rapid and sustained increase (P<0.05) in ENK mRNA in ipsilateral piriform cortex (from 3 h to 2 days; 70-250% above contralateral), and a delayed increase in caudate putamen and olfactory tubercle at 1 and 2 days ( approximately 25% in both regions), but levels were again equivalent to control at 7 days and beyond. In contrast, no marked changes in neocortical ENK mRNA, or DYN mRNA in both cortex and basal ganglia, were observed under these conditions. These findings demonstrate that CSD has specific, rapid and long-lasting effects on neuropeptide expression in neocortex and subcortical areas. CSD-induced changes in mesostriatal ENK mRNA are proposed to reflect synaptic activation of local neurons via cortical afferent projections.     

Effects of space flight stress on proopiomelanocortin, proenkephalin A, and tachykinin neuropeptidergic systems in the rat posterior pituitary

beta-endorphin-like immunoreactivity (BE-li), methionine enkephalin-like immunoreactivity (ME-li), and substance P-like immunoreactivity (SP-li) were measured in the posterior pituitary of rats that experienced a 5-day space flight in a Space Shuttle. ME-li and SP-li were both significantly lower compared to the control rats. However, there was no difference in BE-li between flight and control rats. These data suggest that the space flight stress diminished the methionine enkephalin (ME) and substance P (SP) concentrations in the posterior pituitary without affecting the beta-endorphin (BE) concentration. Thus, the proenkephalin A and tachykinin, but not proopiomelanocortin, neuropeptidergic systems in the posterior pituitary may respond to this type of unique stress.     

Alterations in hypothalamic mu-opiate receptor-mediated responses but not methionine enkephalin or proenkephalin messenger RNA levels in rats with acute cholestasis

Endogenous opioids, including methionine enkephalin, have been implicated in the control of adrenocorticotrophic hormone release by acting through mu-opiate receptors in the hypothalamus. Recently, alterations in the central opioid system have been postulated to occur in cholestasis. In addition, alterations in hypothalamic corticotropin-releasing hormone content and messenger RNA levels, as well as basal release, have been described in bile duct-resected rats, and hypothalamic methionine enkephalin is colocalized with corticotropin-releasing hormone in hypothalamic neurons. Therefore hypothalamic and pituitary methionine enkephalin content and hypothalamic proenkephalin messenger RNA levels, as well as hypothalamic mu-opiate receptor-mediated responses in vitro and in vivo, were studied in rats with acute cholestasis caused by bile duct resection and in respective controls. Hypothalamic and pituitary methionine enkephalin levels were similar in bile duct-resected, sham-resected and unoperated control rats. In addition, hypothalamic proenkephalin steady state messenger RNA levels were similar in the three groups of animals. mu-Opiate receptor stimulation of hypothalamic explants in vitro with the specific mu-opiate receptor agonist ligand [D-Ala2,N-Me-Phe4,Gly-ol]-Enkephalin resulted in 8.2% and 16.9% inhibition of corticotropin-releasing hormone release in sham-resected and unoperated control rats, respectively. In contrast, treatment of hypothalamic explants from bile duct-resected rats with [D-Ala2,N-Me-Phe4,Gly-ol]-Enkephalin resulted in a significant 22.5% increase in corticotropin-releasing hormone release. Systemic administration of the mu-opiate receptor agonist morphine to rats in vivo resulted in significantly higher incremental rises in plasma adrenocorticotropic hormone levels in sham-resected and unoperated control animals than in bile duct-resected rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunohistochemical localization of enkephalin in peripheral sensory axons in the rat

Impaired energy metabolism plays an important role in neuronal cell death after brain ischemia, and apoptosis has been implicated in cell death induced by metabolic impairment. In the present study, metabolic impairment was induced by 3-nitropropionic acid (3-NP), an irreversible inhibitor of succinate dehydrogenase. In order to clarify the involvement of poly(ADP-ribosyl)ation and apoptotic pathway in 3-NP induced cell death, we examined poly(ADP-ribosyl)ation and the apoptosis related gene protein expression after systemic administration of 3-NP by immunohistochemistry. Poly(ADP-ribosyl)ation was evidently detected in the striatal lesion but not in any other region. Immunoreactive ratio of Bcl-2 to Bax significantly increased both in the striatum and cortex. The data suggest that striatal cell death involves poly(ADP-ribosyl)ation and also apoptotic pathway in part following administration of 3-NP.     

Aging and regression of cardiac hypertrophy in the hypertensive patient

OBJECTIVE: This study was aimed at determining factors acting on the regression of left ventricular hypertrophy due to essential hypertension. METHODS: It was a non-randomized, echocardiographic study of 60 previously untreated hypertensive subjects (20 to 75 years of age). RESULTS: Following a 5-year therapy, the decrease in the left ventricular mass was 14%. Normalization of blood pressure and reversal of left ventricular hypertrophy were obtained in 50% and 58% of patients, respectively. Patients of the non-responder group (non-response being defined as a less than 10% decrease in the left ventricular mass) were older and had a longer history of high blood pressure. A positive correlation was observed between age and decrease in the left ventricular mass, the latter being less marked in older patients. Antihypertensive drugs classes had no influence on reversal of left ventricular hypertrophy. CONCLUSION: Ageing may be a factor of resistance to the decrease in left ventricular mass with therapy. These results suggest that early screening and management of hypertension are essential.     

Associative fear conditioning of enkephalin mRNA levels in central amygdalar neurons.

The central nucleus of the amygdala (CEA) is required for the expression of learned fear responses. This study used in situ hybridization to show that mRNA levels of the neuropeptide enkephalin are increased in CEA neurons after rats are placed in an environment that they associate with an unpleasant experience. In contrast, mRNA levels of another neuropeptide, corticotropin releasing hormone, do not change under the same conditions in the CEA of the same rats. Conditioned neuropeptide levels in amygdalar circuits may act as a reversible "gain control" for long-term modulation of subsequent fear responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the bioactive form and molecular determinants of recognition of cyclic enkephalin peptides at the delta-opioid receptor

An extensive and systematic search strategy to determine the conformational profile of 12 cyclic disulfide-bridged opioid peptides with varying affinities at the delta receptor has been carried out to identify the structure that is recognized by the delta receptor for each analogue. The methods and procedures used here for the conformational search have already been validated for [D-Pen2,D-Pen5] enkephalin (DPDPE), one member of this family. Use of these methods led to a low-energy solution conformation of DPDPE in excellent agreement with all the geometric properties deduced from its solution nmr spectra. Each of the analogue was subjected to the same procedure, involving a combination of molecular dynamics simulations at high and low temperature. The study was repeated in two environmental conditions, an apolar environment, simulated by using a distance-dependent dielectric constant, and a polar environment by embedding the peptides in a high constant dielectric (epsilon = 80). An automated comparison of the different conformers based on their backbone rms and average distance between the key aromatic moieties was followed by graphic analysis using maximum structural overlap. The cross-comparison of the conformations for each analogue revealed a unique conformer that may be recognized by the delta receptor for each high-affinity analogue that permitted maintaining the critical elements required for recognition in a simple spatial orientation, while maximizing similarity in other regions.     

Temporal changes in spinal cord expression of mRNA for substance P, dynorphin and enkephalin in a model of chronic pain

We have used a partial sciatic nerve ligation model to examine the time course for changes in the expression of mRNA for three peptides related to pain transmission at spinal sites (dynorphin, enkephalin and substance P), during the development of allodynia. Enhanced expression of mRNA for dynorphin and substance P was observed in the dorsal horn on the same side as the partial nerve ligation. Increased expression of dynorphin mRNA was biphasic. The initial increases in expression of dynorphin mRNA occurred at 3 h, and a secondary peak was observed 1-3 days after surgery. The secondary increases coincided roughly with increased substance P mRNA expression. However, both dynorphin and substance P mRNA returned to control values after 1 week despite continuing allodynia. No significant changes in expression of mRNA for enkephalin were observed. The elevation of substance P mRNA in intrinsic spinal cord neurons may be secondary to changes in immediate early genes c-fos and jun-B, whereas the expression of dynorphin and enkephalin mRNA is differently regulated. The results also suggest that changes in the expression of the three neuropeptides are not critically involved in the development and maintenance of chronic pain or allodynia.     

Microtubules are needed for dispersal of alpha-myosin heavy chain mRNA in rat neonatal cardiac myocytes

In some cell types, microtubules are used for transport of mRNA through the cytoplasm to the translation site. The number of microtubules increases during growth of cardiac myocytes, suggesting a functional role exists. Here, we test the need for microtubules to transport alpha-myosin heavy chain (alpha-MyHC) mRNA through the cytoplasm of neonatal cardiac myocytes. The alpha-MyHC mRNA concentration was assessed by non-radioactive in situ hybridization. The relative mRNA distributions were expressed as slopes (m=OD/micrometer), since optical density declined linearly from the nucleus to the cell periphery. Spontaneously-contracting myocytes displayed a gradual decrease in alpha-MyHC mRNA away from the nucleus (m=-1.27+/-0.12 OD/micrometer). To test whether microtubules were necessary for alpha-MyHC mRNA dispersal, contraction was first arrested with the Ca2+-channel blocker verapamil (10 micrometer) for 18 h, which aggregated the mRNA perinuclearly. Contractile activity was then resumed by washing out verapamil and using isoproterenol (10 micrometer) in the presence or absence of a microtubule depolymerizing drug, colchicine (3 micrometer). Within 6 h, the alpha-MyHC mRNA distribution in myocytes with microtubules returned to normal values (m=-1.11+/-0.14 OD/micrometer), while cells lacking microtubules maintained a perinuclear mRNA distribution (m-1.50+/-0.16 OD/micrometer; P<0.05 from control). Despite this perinuclear pattern of mRNA distribution, the myocytes still produced new myofibrils. These data indicate that microtubules are necessary for dispersal of alpha-MyHC mRNA outward from the nucleus. Furthermore, myofibrillogenesis may occur independently of mRNA localization and microtubule organization.     

Hypothalamic-pituitary-adrenal axis activity in the inbred Brown Norway and Fischer 344 rat strains

We have examined the basal and the stress-induced secretion of corticosterone in relation to the expression of adrenal steroid receptors in the pituitary, hypothalamus and hippocampus of the inbred Brown Norway and Fischer 344 rat strains. Our data indicated that plasma transcortin and integrated plasma corticosterone levels were significantly higher in Fischer 344 compared to Brown Norway rats. Fischer 344 hypersecrete corticosterone during the dark phase of the diurnal cycle and during the phase of recovery following a 20 min period of restraint stress compared to Brown Norway rats. This hypersecretion of corticosterone was negatively correlated with the size of the adrenal gland but might be related to the higher density of mineralocorticoid receptors in the hippocampus of Fischer 344 rats.     

RU-486 blocks stress-induced enhancement of proenkephalin gene expression in the paraventricular nucleus of rat hypothalamus

The purpose of this study was to investigate the glucocorticoid (GC) mediated regulation of corticotropin-releasing hormone (CRH) and proenkephalin (PE) gene expressions in the paraventricular nucleus (PVN) of the hypothalamus during physical stress induced by a single intraperitoneal (i.p.) injection of hypertonic saline (9% NaCl). Previous intracerebroventricular (i.c.v.) administration of the type II glucocorticoid receptor (GR) antagonist RU-486 (20 ng/rat), increased the basal CRH mRNA levels in the PVN but had no effect on PE gene expression. Stress induced by injection of hypertonic saline increased both CRH and PE mRNA levels in PVN. Administration of RU-486 completely blocked the stress-induced increase of PE mRNA levels, but failed to alter the CRH mRNA levels in the PNV. These data suggests that, under these experimental conditions, endogenous GC are necessary for a normal PE response to hypertonic saline stress.     

Transforming growth factor-alpha in carcinogen-induced F344 rat hepatic foci

Transforming growth factor-alpha (TGF alpha) is a positive growth regulator in epithelial cells, including hepatocytes. Overexpression of TGF alpha has been associated with increased growth and malignancy of end-stage cancers in humans and rodents. The overall aim of this study was to characterize TGF alpha staining in diethylnitrosamine-induced hepatic foci from male F344 rats with the hematoxylin and eosin (H and E) histological phenotype. The association between the individual focal DNA synthesis labeling index and the presence of TGF alpha was also examined. Hepatic foci were identified as eosinophilic, basophilic, clear cell, or mixed cell. Of these foci, 37.5% labeled positive for TGF alpha. There were distinct differences in the pattern of TGF alpha labeling between the different H and E histological phenotypes. Intense, uniform TGF alpha labeling was observed in eosinophilic foci. Basophilic foci labeled for TGF alpha diffusely uniform throughout the cytoplasm. In clear-cell foci, TGF alpha labeling occurred primarily along the periphery of the cell membrane. In mixed-cell foci, labeling occurred both along the periphery and diffusely throughout the cytoplasm. On those slides stained, glutathione-S-transferase (placental; GSTP) was detected in almost all eosinophilic and mixed-cell foci, whereas approximately half of the basophilic and clear-cell foci stained for GSTP. The presence of GSTP in a focus was not always associated with the presence of increased TGF alpha protein. All rat hepatic adenomas and the one carcinoma labeled positive for TGF alpha. Increased levels of TGF alpha protein were associated with increased DNA synthesis labeling index. The number of TGF alpha-positive foci with the highest DNA synthesis labeling indices were statistically higher than those with lower levels of DNA synthesis labeling. Although characteristic staining patterns for TGF alpha were associated with specific histological subtype, the role that TGF alpha plays in the progression of focal lesions to neoplasia requires further definition. High levels of TGF alpha protein appear to be acquired sometime during the hepatocarcinogenic process. It may be that early lesions that acquire high levels of TGF alpha are the ones to develop into hepatocellular carcinoma (e.g., hepatocellular carcinoma is determined very early in the carcinogenic process). It is apparent that further work is needed to delineate the role of TGF alpha in both rodent and human hepatocarcinogenesis.     

Adrenal neuropeptide Y mRNA but not preproenkephalin mRNA induction by stress is impaired by aging in Fischer 344 rats

The purpose of this study was to examine factors predicting the practice of breast self-examination behaviour among Chinese women in Hong Kong using a cross-sectional survey research design. The Health Belief Model was used as the theoretical framework for the study to examine differences between breast self-examination practicers and non-practicers and among breast self-examination frequency groups. Data were collected from a convenience sample of 124 women using self-administrated questionnaires. Less than half of the sample practised breast self-examination and only 16% of the practicers performing breast self-examination monthly. There were differences between practicers vs. non-practicers and among breast self-examination frequency groups and some support of the predictive power of the Health Belief Model was found. Logistic regression showed that practicers perceived health as important, having fewer barriers and higher susceptibility to breast cancer. Discriminant function analysis revealed that barriers and children status were strong predictors of frequency of breast self-examination practice explaining 21.1% of the total variance in breast self-examination practice.