Microinjections of urocortin1 into the nucleus ambiguus of the rat elicit bradycardia

Urocortins are members of the hypothalamic corticotropin-releasing factor (CRF) peptide family. Urocortin1 (UCN1) mRNA has been reported to be expressed in the brainstem neurons. The present investigation was carried out to test the hypothesis that microinjections of UCN1 into the nucleus ambiguus (nAmb) may elicit cardiac effects. Urethane-anesthetized, artificially ventilated, adult male Wistar rats, weighing between 300–350 g, were used. nAmb was identified by microinjections of l-glutamate (5 mM, 30 nl). Microinjections (30 nl) of different concentrations (0.062, 0.125, 0.25, and 0.5 mM) of UCN1 into the nAmb elicited bradycardic responses (26.5 ± 1, 30.1 ± 1.7, 46.9 ± 1.7, and 40.3 ± 2.6 beats/min, respectively). These heart rate responses were not accompanied by significant changes in mean arterial pressure. The bradycardic responses to maximally effective concentration of UCN1 (0.25 mM) were significantly ( P < 0.05) attenuated by prior microinjections of a selective antagonist (NBI 27914, 1.5 mM) for CRF type 1 receptor (CRF1R). Prior microinjections of ionotropic glutamate receptor (iGLUR) antagonists [d-(−)-2-amino-7-phosphono-heptanoic acid and 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo-(f)quinoxaline-7-sulfonamide disodium] also attenuated the bradycardia elicited by UCN1 microinjections into the nAmb. Microinjections of NBI 27914 (1.5 mM) into the nAmb did not alter baroreflex responses. Bilateral vagotomy abolished the bradycardic responses to microinjections of UCN1 into the nAmb. These results indicated that 1) microinjections of UCN1 into the nAmb elicited bradycardia, 2) the bradycardia was vagally mediated, 3) activation of CRF1Rs in the nAmb was responsible for the actions of UCN1, and 4) activation of iGLURs in the nAmb also participated in the bradycardia elicited by UCN1.

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Microinjections of α-melanocyte stimulating hormone into the nucleus ambiguus of the rat elicit vagally mediated bradycardia

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.90978.2008 ◽

2009 ◽

Vol 296 (5) ◽

pp. R1402-R1411 ◽

Cited By ~ 13

Author(s):

Vineet C. Chitravanshi ◽

Suresh Bhatt ◽

Hreday N. Sapru

Keyword(s):

Heart Rate ◽

Cerebrospinal Fluid ◽

Wistar Rats ◽

Direct Application ◽

Nucleus Ambiguus ◽

Melanocyte Stimulating Hormone ◽

Artificial Cerebrospinal Fluid ◽

Male Wistar Rats ◽

Bilateral Vagotomy ◽

Stimulating Hormone

Neurons that immunostain for alpha-melanocyte stimulating hormone (α-MSH) have been identified in the nucleus ambiguus (nAmb). The presence of mRNA for melanocortin type 4 receptors (MC4Rs) has also been reported in this nucleus. On the basis of this information, it was hypothesized that activation of MC4Rs in the nAmb may play a role in the regulation of cardiac function. This hypothesis was tested in urethane-anesthetized, artificially ventilated, adult male Wistar rats. Microinjections (30 nl) of α-MSH (0.1, 0.2, 0.4, 0.8, and 1.2 mM) into the nAmb of anesthetized rats elicited decreases in heart rate (HR; 1.3 ± 0.6, 3 ± 1, 11 ± 2, 46.3 ± 3, and 43.3 ± 7 bpm, respectively) and no changes in mean arterial pressure (MAP). Maximum decreases in HR were elicited by 0.8 mM concentration of α-MSH. Bradycardic responses to α-MSH were similar in unanesthetized midcollicular decerebrate rats. Microinjections of artificial cerebrospinal fluid (30 nl) into the nAmb did not elicit a HR response. Bilateral vagotomy completely abolished α-MSH-induced bradycardia. The decreases in HR elicited by α-MSH (0.8 mM) were completely blocked by a selective MC4R antagonist. Direct application of α-MSH on the nAmb neurons increased their firing, which was blocked by prior applications of the MC4R antagonist. Microinjections of the MC4R antagonist into the nAmb did not alter reflex bradycardic responses elicited by intravenous infusions of phenylephrine, suggesting that MC4Rs did not play a role in mediating the parasympathetic component of baroreflex-induced bradycardia. These results indicated that α-MSH microinjections into the nAmb exert excitatory effects on parasympathetic preganglionic nAmb neurons via MC4Rs, leading to bradycardic responses.

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Cardiac effects of hypocretin-1 in nucleus ambiguus

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00719.2002 ◽

2003 ◽

Vol 284 (6) ◽

pp. R1611-R1620 ◽

Cited By ~ 37

Author(s):

John Ciriello ◽

Cleusa V. R. de Oliveira

Keyword(s):

Wistar Rats ◽

Baroreceptor Reflex ◽

Nucleus Ambiguus ◽

Medullary Reticular Formation ◽

Reflex Bradycardia ◽

Male Wistar Rats ◽

Series Of Experiments ◽

Neuronal Systems ◽

Direct Change ◽

Hypocretin 1

Although recent studies have reported hypocretin 1 (hcrt-1)-like-immunoreactivity (ir) within the region of the nucleus ambiguus (Amb) in the caudal brain stem, the function of hcrt-1 in the Amb on cardiovascular function is not known. Three series of experiments were done in male Wistar rats to investigate the effects of microinjections of hcrt-1 into Amb on heart rate (HR), mean arterial pressure (MAP), and the arterial baroreceptor reflex. In the first series, a detailed mapping of the distribution of hcrt-1- and hcrt-1 receptor (hcrtR-1)-like-ir was obtained of the Amb region. Although hcrt-1-like- and hcrtR-1-like-ir were found throughout the rostrocaudal extent of the Amb and adjacent ventrolateral medullary reticular formation, most of the hcrtR-1-like-ir was observed in the area just ventral to the compact formation of Amb, in the region of the external formation of the nucleus (Ambe). In the second series, the Amb region that contained hcrt-1 and hcrtR-1-ir was explored for sites that elicited changes in HR and MAP in urethane and α-chloralose-anesthetized rats. Microinjections of hcrt-1 (0.5–2.5 pmol) into the Ambe elicited a dose-related decrease in HR, with little or no direct change in MAP. The small decreases in MAP were found to be secondary to the HR changes. The largest bradycardia responses were elicited from sites in the Ambe. Administration (iv) of the muscarinic receptor antagonist atropine methyl bromide or ipsilateral vagotomy abolished the HR response, indicating that the HR response was due to activation of vagal cardiomotor neurons. In the final series, microinjections of hcrt-1 into the Ambe significantly potentiated the reflex bradycardia elicited by activation of the baroreflex as a result of the increased MAP after the intravenous injection of phenylephrine. These data suggest that hcrt-1 in the Ambe activates neuronal systems that alter the excitability of central circuits that reflexly control the circulation through the activation of vagal preganglionic cardioinhibitory neurons.

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GABA and glycine receptors in the nucleus ambiguus mediate tachycardia elicited by chemical stimulation of the hypothalamic arcuate nucleus

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00801.2014 ◽

2015 ◽

Vol 309 (1) ◽

pp. H174-H184 ◽

Cited By ~ 5

Author(s):

Vineet C. Chitravanshi ◽

Kazumi Kawabe ◽

Hreday N. Sapru

Keyword(s):

Paraventricular Nucleus ◽

Wistar Rats ◽

Arcuate Nucleus ◽

Chemical Stimulation ◽

Nucleus Ambiguus ◽

Glycine Receptors ◽

Inhibitory Neurotransmitters ◽

Hypothalamic Arcuate Nucleus ◽

Male Wistar Rats ◽

Stimulation Of

We have previously reported that stimulation of the hypothalamic arcuate nucleus (ARCN) by microinjections of N-methyl-d-aspartic acid (NMDA) elicits tachycardia, which is partially mediated via inhibition of vagal inputs to the heart. The neuronal pools and neurotransmitters in them mediating tachycardia elicited from the ARCN have not been identified. We tested the hypothesis that the tachycardia elicited from the ARCN may be mediated by inhibitory neurotransmitters in the nucleus ambiguus (nAmb). Experiments were done in urethane-anesthetized, artificially ventilated, male Wistar rats. In separate groups of rats, unilateral and bilateral microinjections of muscimol (1 mM), gabazine (0.01 mM), and strychnine (0.5 mM) into the nAmb significantly attenuated tachycardia elicited by unilateral microinjections of NMDA (10 mM) into the ARCN. Histological examination of the brains showed that the microinjections sites were within the targeted nuclei. Retrograde anatomic tracing from the nAmb revealed direct bilateral projections from the ARCN and hypothalamic paraventricular nucleus to the nAmb. The results of the present study suggest that tachycardia elicited by stimulation of the ARCN by microinjections of NMDA is mediated via GABAA and glycine receptors located in the nAmb.

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Delayed stress-induced colonic hypersensitivity in male Wistar rats: role of neurokinin-1 and corticotropin-releasing factor-1 receptors

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00358.2003 ◽

2004 ◽

Vol 286 (4) ◽

pp. G683-G691 ◽

Cited By ~ 57

Author(s):

Ines Schwetz ◽

Sylvie Bradesi ◽

James A. McRoberts ◽

Marciano Sablad ◽

Jerry C. Miller ◽

...

Keyword(s):

Nervous System ◽

Sympathetic Nervous System ◽

Wistar Rats ◽

Corticotropin Releasing Factor ◽

Chemical Sympathectomy ◽

Visceromotor Response ◽

Male Wistar Rats ◽

Sympathetic Nervous ◽

Neurokinin 1

The mechanism(s) underlying stress-induced colonic hypersensitivity (SICH) are incompletely understood. Our aims were to assess the acute and delayed (24 h) effect of water avoidance (WA) stress on visceral nociception in awake male Wistar rats and to evaluate the role of two stress-related modulation systems: the substance P/neurokinin-1 receptor (SP/NK1R) and the corticotropin-releasing factor (CRF)/CRF1 receptor (CRF/CRF1R) systems, as well as the possible involvement of the sympathetic nervous system. Visceral pain responses were measured as the visceromotor response to colorectal distension (CRD) at baseline, immediately after WA and again 24 h later. The NK1R antagonists RP-67580 and SR-140333 and the CRF1R antagonist CP-154526 were injected 15 min before WA or 1 h before the CRD on day 2. Chemical sympathectomy was performed by repeated injection of 6-hydroxydopamine. WA stress resulted in a significant increase in the visceromotor response on day 2, but no change immediately after WA. Injection of CP-154526 abolished delayed SICH when applied either before WA stress or before the CRD on day 2. Both NK1R antagonists only decreased SICH when injected before the CRD on day 2. Chemical sympathectomy did not affect delayed SICH. Our results indicate that in male Wistar rats, both NK1R and CRF1R activation, but not sympathetic nervous system activation, play a role in the development of SICH.

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Teneurin C-terminal associated peptide (TCAP)-1 attenuates corticotropin-releasing factor (CRF)-induced c-Fos expression in the limbic system and modulates anxiety behavior in male Wistar rats

Behavioural Brain Research ◽

10.1016/j.bbr.2009.02.013 ◽

2009 ◽

Vol 201 (1) ◽

pp. 198-206 ◽

Cited By ~ 19

Author(s):

Laura A. Tan ◽

Karen Xu ◽

Franco J. Vaccarino ◽

David A. Lovejoy ◽

Susan Rotzinger

Keyword(s):

Limbic System ◽

Wistar Rats ◽

Corticotropin Releasing Factor ◽

Male Wistar Rats ◽

Anxiety Behavior ◽

Fos Expression

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Effects of sub-chronic exposure to palladium (as potassium hexachloro-palladate) on cytokines in male Wistar rats

Human & Experimental Toxicology ◽

10.1177/0960327108090489 ◽

2008 ◽

Vol 27 (6) ◽

pp. 493-497 ◽

Cited By ~ 12

Author(s):

I Iavicoli ◽

G Carelli ◽

A Marinaccio ◽

L Fontana ◽

EJ Calabrese

Keyword(s):

Chronic Exposure ◽

Wistar Rats ◽

Statistical Significance ◽

Response Relationship ◽

Dose Response Relationship ◽

Mean Values ◽

Male Wistar Rats ◽

The Difference

Palladium (Pd) is a heavy metal belonging to the platinum group elements. It has been shown that Pd and its compounds can cause sensitization, asthma and dermatologic disorders. In this study, Wistar rats were exposed for 3 months to 0, 1, 10, 100, and 250 ng/ml of Pd (as potassium hexachloro-palladate) in drinking water. At the end of exposure, possible changes in two type-1 cytokines [interleukin (IL)-2, interferon (INF)-γ] and one type-2 cytokine (IL-4) in the serum were measured. After the sub-chronic exposure, analysis of variance of IL-2 and INF-γ response shows that the difference between mean values in the groups of animals exposed reaches statistical significance for IL-2 ( P = 0.001), showing a J-shaped dose–response relationship. At the higher dose of 250 ng/ml Pd, it was observed a significant increase in IL-2 production when compared with the controls. Furthermore at 1 and 10 ng/ml of Pd we observed an increase of INF-γ production that was significant at 100 ng/ml of Pd, while at the higher dose of 250 ng/ml of Pd the response was indistinguishable from the control. At the doses investigated, Pd has been shown not to determine a modification of IL-4 response ( P = 0.10). These preliminary findings indicate the need to carry out further investigations regarding the effect of other Pd compounds and the measurement of other types of cytokines both in the animal model used in our study and other models.

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The B-vitamin group and the activity of hepatic microsomal mixed-function oxidases of the growing Wistar rat

British Journal Of Nutrition ◽

10.1079/bjn19780019 ◽

1978 ◽

Vol 39 (1) ◽

pp. 127-137 ◽

Cited By ~ 5

Author(s):

R. Miltenberger ◽

U. Oltersdorf

Keyword(s):

Wistar Rats ◽

Wistar Rat ◽

B Vitamins ◽

Vitamin B ◽

Microsomal Enzymes ◽

Mixed Function Oxidases ◽

Male Wistar Rats ◽

B Vitamin ◽

Hepatic Microsomal Enzymes

1. Male Wistar rats were given isoenergetic, semi-synthetic diets deficient in thiamin, riboflavin, pyrid-oxine or all the B-vitamins.2. In rats given these deficient diets the ‘sleeping time’ induced with pentobarbital (PB) and the ‘paralysis time’ with zoxazolamine (Zz) were prolonged.3. The tolerance effect against both drugs was nearly independent of the levels of B-vitamins in the diets.4. In preparations from vitamin-B deficient animals the activities of the following hepatic microsomal enzymes were reduced: the aliphatic hydroxylase of PB, the aromatic hydroxylases of aniline (EC 1.14.14.1) and of Zz, the N-demethylase of aminopyrine, the UDP glucuronyltransferase (EC 2.4.1.17) of p-nitrophenol. The reactions most influenced were those of ‘type-1’ substrates, particularly those involving the hydroxylases.5. The effects observed were caused mainly by deficiency of riboflavin and to a lesser extent of thiamin or pyridoxine.

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