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Lee SW, Lee H, Yoo J, Kim J, Lim KB. Sick Sinus Syndrome Combined with Wallenberg Syndrome: a Case Report. BRAIN & NEUROREHABILITATION 2021; 14:e27. [PMID: 36741224 PMCID: PMC9879381 DOI: 10.12786/bn.2021.14.e27] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/29/2021] [Accepted: 10/11/2021] [Indexed: 11/08/2022] Open
Abstract
Cardiac arrhythmia is a rare manifestation of the Wallenberg syndrome; lesions are located in the brainstem, especially the lower medulla, which regulates sympathetic and parasympathetic activity. A 55-year-old man was admitted to the university hospital with symptoms including ataxia, left ptosis, decreased sensation of pain and temperature on the right side, left facial numbness, and dizziness. Brain magnetic resonance imaging revealed an infarction in the left dorsolateral medulla. Therefore, he was diagnosed with Wallenberg syndrome. While he underwent conservative treatment for Wallenberg syndrome, he experienced several events of self-limiting heart pounding, which required an evaluation of cardiac function. The 24-hour Holter monitor showed an increased RR interval with bradycardia and prolonged sinus pause. As a result, the diagnosis of sick sinus syndrome combined with Wallenberg syndrome was made. Sick sinus syndrome is a rare cardiac complication of the Wallenberg syndrome, and clinicians could overlook it when the initial electrocardiography shows a normal sinus rhythm. Sick sinus syndrome can cause sudden death without appropriate medical intervention. Therefore, clinicians should consider further evaluation, including a 24-hour Holter monitor, to check for the potential presence of sick sinus syndrome in the acute phase of Wallenberg syndrome.
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Affiliation(s)
- Sang Wan Lee
- Department of Physical Medicine and Rehabilitation, Inje University Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
| | - Hojin Lee
- Department of Physical Medicine and Rehabilitation, Inje University Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
| | - Jeehyun Yoo
- Department of Physical Medicine and Rehabilitation, Inje University Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
| | - Jiyong Kim
- Department of Physical Medicine and Rehabilitation, Inje University Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
| | - Kil-Byung Lim
- Department of Physical Medicine and Rehabilitation, Inje University Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
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Iwasa M, Kawabe K, Sapru HN. Activation of melanocortin receptors in the intermediolateral cell column of the upper thoracic cord elicits tachycardia in the rat. Am J Physiol Heart Circ Physiol 2013; 305:H885-93. [PMID: 23832700 DOI: 10.1152/ajpheart.00443.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Melanocortin receptors (MCRs) are present in the intermediolateral cell column of the spinal cord (IML). We tested the hypothesis that activation of MCRs in the IML elicits cardioacceleratory responses and the source of melanocortins in the IML may be the melanocortin-containing neurons in the hypothalamic arcuate nucleus (ARCN). Experiments were done in urethane-anesthetized, artificially ventilated adult male Wistar rats. Microinjections (50 nl) of α-melanocyte stimulating hormone (α-MSH) (0.4-2 mM) and adrenocorticotropic hormone (ACTH) (0.5-2 mM) into the right IML elicited increases in heart rate (HR). These tachycardic responses were blocked by microinjections of melanocortin receptor 4 (MC4R) antagonists [SHU9119 (0.25 mM) or agouti-related protein (AGRP, 0.1 mM)] into the right IML. Stimulation of right ARCN by microinjections (30 nl) of N-methyl-d-aspartic acid (NMDA, 10 mM) elicited increases in HR. Blockade of MC4Rs in the ipsilateral IML at T1-T3 using SHU9119 (0.25 mM) attenuated the tachycardic responses elicited by subsequent microinjections of NMDA into the ipsilateral ARCN. ARCN neurons retrogradely labeled by microinjections of Fluoro-Gold into the right IML showed immunoreactivity for proopiomelanocortin (POMC), α-MSH, and ACTH. Fibers immunoreactive for POMC, α-MSH, and ACTH were present in the IML at T1-T3. These results indicated that activation of MC4Rs in the right IML elicited tachycardia and one of the sources of melanocortins in the IML is the ARCN. Melanocortin levels are elevated in stress and ARCN neurons are activated during stress. Our results allude to the possibility that cardiac effects of stress may be mediated via melanocortin containing ARCN neurons that project to the IML.
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Affiliation(s)
- Masamitsu Iwasa
- Department of Neurological Surgery, Rutgers, New Jersey Medical School, Newark, New Jersey
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Ward KR, Bardgett JF, Wolfgang L, Stocker SD. Sympathetic response to insulin is mediated by melanocortin 3/4 receptors in the hypothalamic paraventricular nucleus. Hypertension 2011; 57:435-41. [PMID: 21263116 DOI: 10.1161/hypertensionaha.110.160671] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hyperinsulinemia increases sympathetic nerve activity and contributes to cardiovascular dysfunction in obesity and diabetes. Neurons of the hypothalamic paraventricular nucleus (PVN) regulate sympathetic nerve activity through mono- and poly-synaptic connections to preganglionic neurons in the spinal cord. The purpose of the present study was to determine whether PVN neurons mediate the sympathetic response to insulin. Hyperinsulinemic-euglycemic clamps were performed in α-chloralose-anesthetized, male Sprague-Dawley rats (280-420 g) by an infusion of insulin (3.75 mU/kg per min) and 50% dextrose (0.75-2.0 mL/h) for 120 minutes. At 90 minutes, insulin significantly increased lumbar sympathetic nerve activity without any change in renal sympathetic nerve activity, heart rate, or blood glucose levels. Inhibition of the PVN with bilateral injection of the GABA(A) receptor agonist muscimol completely reversed the sympathoexcitatory response. However, direct injection of insulin into the PVN did not alter lumbar sympathetic nerve activity, and thereby suggests that insulin activates neurons upstream of the PVN. Interestingly, the sympathetic response to insulin was eliminated by PVN injection of the melanocortin 3/4 receptor antagonist SHU9119, but was unaffected by the angiotensin II type 1 receptor antagonist losartan. A final set of experiments suggests activation of PVN neurons during hyperinsulinemia increases glutamatergic drive to the rostral ventrolateral medulla. Collectively, these findings indicate that insulin activates a melanocortin-dependent pathway to the PVN that increases glutamatergic drive to the rostral ventrolateral medulla and alters cardiovascular function.
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Affiliation(s)
- Kathryn R Ward
- Department of Cellular & Molecular Physiology, Penn State College of Medicine, Hershey, PA 17033, USA
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Skibicka KP, Grill HJ. Hypothalamic and hindbrain melanocortin receptors contribute to the feeding, thermogenic, and cardiovascular action of melanocortins. Endocrinology 2009; 150:5351-61. [PMID: 19854868 PMCID: PMC2795709 DOI: 10.1210/en.2009-0804] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Forebrain ventricular delivery of melanocortin receptor (MC3/4R) agonist increases energy expenditure and decreases food intake (FI). Because forebrain ventricular delivery provides ligand to various anatomically distributed MC3/4R-bearing nuclei, it is unclear which of the receptor subpopulations contributes to the feeding suppression and the sympathetic-thermogenic effects observed. The literature indicates that reexpression of MC4R in the paraventricular nucleus (PVH) affects the feeding but not the energetic phenotype of the MC4R knockout, suggesting that divergent MC4R populations mediate energy expenditure (hindbrain) and FI (hypothalamus) effects of stimulation. Not consistent with this view are data indicating that PVH sympathetic projection neurons express MC4Rs and that feeding effects are induced from hindbrain MC4R sites. Therefore, we hypothesize an opposing perspective: that stimulation of anatomically diverse MC3/4R-bearing nuclei triggers energetic as well as feeding effects. To test this hypothesis, ventricle subthreshold doses of MC3/4R agonist (5 and 10 pmol) were applied in separate experiments to six hindbrain and hypothalamic sites; core temperature (Tc), heart rate (HR), spontaneous activity (SPA), and FI were measured in behaving rats. Nucleus tractus solitarius and PVH stimulation increased Tc, HR, and SPA and decreased FI. Rostral ventrolateral medulla, parabrachial nucleus, and retrochiasmatic area stimulation increased Tc, HR, but not SPA, and decreased FI. The response profile differed to some extent for each nucleus tested, suggesting differential output circuitries for the measured parameters. Data are consistent with the view that energetic and feeding responses are not controlled by regionally divergent MC3/4Rs and can be elicited from multiple, anatomically distributed MC3/4R populations.
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Affiliation(s)
- Karolina P Skibicka
- Graduate Group of Psychology and Graduate Group of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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von Heinemann P, Grauer O, Schuierer G, Ritzka M, Bogdahn U, Kaiser B, Schlachetzki F. Recurrent cardiac arrest caused by lateral medulla oblongata infarction. BMJ Case Rep 2009; 2009:bcr02.2009.1625. [PMID: 21991295 DOI: 10.1136/bcr.02.2009.1625] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Cardiac arrest is a rare complication in Wallenberg syndrome, despite the fact that the brainstem, especially the lower medulla, modulates sympathetic and parasympathetic activity. In the case reported here, a 45-year-old man was admitted with clinical symptoms of Wallenberg syndrome, including right sided hemiparesis secondary to dissection of the right vertebral artery. During the following days he experienced several spells of self limiting cardiac arrests, which made the implantation of a pacemaker necessary. Magnetic resonance imaging scan showed an infarction on the lower right and dorsolateral medulla. This might have affected the central sympathetic neurons which normally inhibit the nucleus of the solitary tract. The disinhibition of the nucleus tractus solitarii may have led to an increase of parasympathetic outflow resulting in bradycardia/asystolia. This case report describes a rare indication for transient or permanent therapy with a cardiac pacemaker in Wallenberg syndrome.
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Affiliation(s)
- Philipp von Heinemann
- University of Regensburg, Neurology, Universitaetsstr.84, Regensburg, 93053, Germany
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Chitravanshi VC, Bhatt S, Sapru HN. Microinjections of alpha-melanocyte stimulating hormone into the nucleus ambiguus of the rat elicit vagally mediated bradycardia. Am J Physiol Regul Integr Comp Physiol 2009; 296:R1402-11. [PMID: 19297540 DOI: 10.1152/ajpregu.90978.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurons that immunostain for alpha-melanocyte stimulating hormone (alpha-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 alpha-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 alpha-MSH. Bradycardic responses to alpha-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 alpha-MSH-induced bradycardia. The decreases in HR elicited by alpha-MSH (0.8 mM) were completely blocked by a selective MC4R antagonist. Direct application of alpha-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 alpha-MSH microinjections into the nAmb exert excitatory effects on parasympathetic preganglionic nAmb neurons via MC4Rs, leading to bradycardic responses.
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Affiliation(s)
- Vineet C Chitravanshi
- Department of Neurological Surgery, University of Medicine and Dentistry-New Jersey Medical School, Newark, N.J. 07103, USA
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Thomale UW, Tyler B, Renard VM, Dorfman B, Guarnieri M, Haberl HE, Jallo GI. Local chemotherapy in the rat brainstem with multiple catheters: a feasibility study. Childs Nerv Syst 2009; 25:21-8. [PMID: 18690465 DOI: 10.1007/s00381-008-0684-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Indexed: 11/25/2022]
Abstract
OBJECTS Technical aspects of local chemotherapy in inoperable brainstem gliomas by convection-enhanced delivery (CED) are still under experimental considerations. In this study, we characterize the feasibility of multiple cannula placements in the rat brainstem. MATERIALS AND METHODS In 38 male Fisher rats, up to three guided screws were positioned in burr holes paramedian at 2.5 mm anterior and posterior to as well as at the lambdoid suture. Using Alzettrade mark pumps (1 microl/h flow rate over 7 days) either vehicle (5% dextrose) or 0.1 mg carboplatin was delivered via one, two, or three cannulas, respectively. During cannula insertion, electrocardiogram and respiratory rate was monitored. All rats were subsequently evaluated neurologically for 8 days. For drug distribution in coronal sections, the brain tissue concentration of platinum was measured. HE staining was used to evaluate the local site of drug delivery. Heart and respiratory rate remained within normal range during surgical procedure. Neurological scoring showed only mild neurological impairment in the groups receiving two or three cannulas, which resolved after vehicle delivery. However, after carboplatin delivery, this deficit remained unchanged. Drug distribution was more homogeneous in the three cannula group. Histological slices visualized edematous changes at the sight of cannula placement. CONCLUSION The unilateral application of up to three cannulas in the brainstem of rats for local drug delivery studies is feasible. The remaining neurological deficit in carboplatin-treated animals underlines the need of low toxicity drugs for CED in the brainstem.
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Affiliation(s)
- U W Thomale
- Selbständiger Arbeitsbereich Pädiatrische Neurochirurgie, Charité, Campus Virchow Klinikum, Universitätsmedizin Berlin, Augustenburgr Platz 1, 13353, Berlin, Germany.
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Sabban EL, Schilt N, Serova LI, Masineni SN, Stier CT. Kinetics and persistence of cardiovascular and locomotor effects of immobilization stress and influence of ACTH treatment. Neuroendocrinology 2009; 89:98-108. [PMID: 18698126 PMCID: PMC2763367 DOI: 10.1159/000150099] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Accepted: 04/22/2008] [Indexed: 11/19/2022]
Abstract
Stress triggers crucial responses, including elevated blood pressure and heart rate (HR), to handle the emergency and restore homeostasis. However, continuation of these effects following cessation of the stress is implicated with many stress-related disorders. Here, we examine the kinetics and persistence of cardiovascular and locomotor responses to single and repeated immobilization stress (IMO), with and without prior treatment with adrenocorticotropic hormone (ACTH). Radiotelemetry probes were implanted into male Sprague-Dawley rats to continually monitor mean arterial pressure (MAP), HR and locomotor activity. Rats were subjected to IMO for 2 h daily (10 a.m. to noon, 6 consecutive days). The first IMO induced the greatest change in MAP (about 30 mm Hg) and HR (about 200 bpm). Following each IMO, MAP and HR were elevated during the remaining light phase and in the subsequent dark phase, HR was lower than prior to IMO. We further examined whether elevation of ACTH to a level similar to IMO will elicit similar effects, and if it will alter subsequent responses to IMO. Injection of ACTH (13 IU/kg, s.c.) triggered a short-lived rise in MAP, and decreased HR. After six daily injections of ACTH and recovery time (8 days), rats were immobilized as above. The cardiovascular responses were similar during the IMO, but the ACTH-pretreated group displayed differences following cessation of the IMO. In addition, IMO led to a large reduction of locomotor activity during the dark (normally active) phase to levels similar to the light phase. Following the IMOs, locomotor activity recovered more slowly in the ACTH-pretreated group. The study revealed that IMO-triggered cardiovascular and locomotor responses are evident after termination of the stress. In addition, prior exposure to ACTH delayed recovery in cardiovascular and locomotor functions following cessation of stress.
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Affiliation(s)
- Esther L Sabban
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, N.Y. 10595, USA.
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Nakamura T, Kawabe K, Sapru HN. Cardiovascular responses to microinjections of urocortin 3 into the nucleus tractus solitarius of the rat. Am J Physiol Heart Circ Physiol 2008; 296:H325-32. [PMID: 19060121 DOI: 10.1152/ajpheart.01044.2008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Urocortin 3 (Ucn3) is a new member of the corticotropin-releasing factor (CRF) peptide family and is considered to be a specific and endogenous ligand for CRF type 2 receptors (CRF2Rs). The presence of CRF(2)Rs has been reported in the nucleus tractus solitarius (NTS) of the rat. It was hypothesized that the activation of CRF2Rs in the medial NTS (mNTS) may play a role in cardiovascular regulation. This hypothesis was tested in urethane-anesthetized, artificially ventilated, adult male Wistar rats. Microinjections (100 nl) of Ucn3 (0.03, 0.06, 0.12, and 0.25 mM) into the mNTS of anesthetized rats elicited decreases in mean arterial pressure (MAP: 5.0 +/- 1.0, 21.6 +/- 2.6, 20.0 +/- 2.8, and 12.7 +/- 3.4 mmHg, respectively) and heart rate (HR: 7.8 +/- 2.6, 46.2 +/- 9.3, 34.5 +/- 8.4, and 16.6 +/- 4.9 beats/min, respectively). Microinjections of artificial cerebrospinal fluid (100 nl) into the mNTS did not elicit cardiovascular responses. Maximum decreases in MAP and HR were elicited by 0.06 mM concentration of Ucn3. Cardiovascular responses to Ucn3 were similar in unanesthetized midcollicular decerebrate rats. A bilateral vagotomy completely abolished Ucn3-induced bradycardia. The decreases in MAP and HR elicited by Ucn3 (0.06 mM) were completely blocked by astressin (1 mM; nonselective CRFR antagonist) and K41498 (5 mM; selective CRF2R antagonist). Microinjections of Ucn3 (0.06 mM) into the mNTS decreased the efferent greater splanchnic nerve activity. After the blockade of CRF2Rs in the mNTS, a Ucn3-induced decrease in the efferent sympathetic nerve discharge was abolished. These results indicate that Ucn3 microinjections into the mNTS exerted excitatory effects on the mNTS neurons via CRF2Rs, leading to depressor and bradycardic responses.
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Affiliation(s)
- Takeshi Nakamura
- Department of Neurological Surgery, UMDNJ-New Jersey Medical School, Newark, NJ, USA
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Serova LI, Gueorguiev V, Cheng SY, Sabban EL. Adrenocorticotropic hormone elevates gene expression for catecholamine biosynthesis in rat superior cervical ganglia and locus coeruleus by an adrenal independent mechanism. Neuroscience 2008; 153:1380-9. [PMID: 18440707 DOI: 10.1016/j.neuroscience.2008.02.059] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 02/25/2008] [Accepted: 02/26/2008] [Indexed: 01/22/2023]
Abstract
Classically, upon hypothalamic stimulation, adrenocorticotropic hormone (ACTH) is released from the pituitary and acts on melanocortin 2 receptors (MC2R) in the adrenal cortex, stimulating glucocorticoid synthesis and release. Our earlier studies suggested that ACTH might have a direct effect on sympathetic ganglia. To analyze further the involvement of ACTH in regulation of gene expression of norepinephrine (NE) biosynthetic enzymes, we examined the effect of bilateral adrenalectomy (ADX) of Sprague-Dawley male rats. Fourteen days post-ADX, as expected, plasma ACTH was elevated, and levels of tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH) and MC2R mRNAs in superior cervical ganglia (SCG), and TH mRNA in locus coeruleus (LC) were increased compared with sham-operated animals. To determine effect of pulsatile elevation of ACTH, corticosterone pellets were implanted to ADX rats. Similar to immobilization (IMO) stress ACTH injections to these animals caused a rise in ACTH in plasma and triggered elevation of TH and DBH mRNAs in SCG and in LC with single and repeated daily injections, and MC2R mRNA in SCG with single injections. To study the effect of ACTH in isolated cells, primary cultures of rat SCG were transfected with TH and DBH promoter constructs and treated with ACTH. In agreement with the in vivo data, ACTH elevated their promoter activities similar to levels triggered by cyclic AMP analog. ACTH in the human SK-N-SH neuroblastoma cells increased TH and DBH promoter activity and endogenous DBH mRNA levels. The results show that ACTH can have a direct effect on transcription and gene expression of NE biosynthetic enzymes even without contribution of adrenal hormones.
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Affiliation(s)
- L I Serova
- Department of Biochemistry and Molecular Biology, Basic Science Building, New York Medical College, Valhalla, NY 10595, USA
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Brown SN, Chitravanshi VC, Kawabe K, Sapru HN. Microinjections of melanin concentrating hormone into the nucleus tractus solitarius of the rat elicit depressor and bradycardic responses. Neuroscience 2007; 150:796-806. [PMID: 17988799 DOI: 10.1016/j.neuroscience.2007.10.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Revised: 09/28/2007] [Accepted: 10/04/2007] [Indexed: 02/07/2023]
Abstract
The presence of melanin-concentrating hormone (MCH) containing processes, projecting from the lateral hypothalamus to the medial nucleus tractus solitarius (mNTS), has been reported in the rat. It was hypothesized that MCH acting within the mNTS may modulate the central regulation of cardiovascular function. This hypothesis was tested in urethane-anesthetized, artificially ventilated, adult male Wistar rats. Microinjections (100 nl) of MCH (0.25, 0.5, 0.75, and 1 mM) into the mNTS of anesthetized rats elicited decreases in mean arterial pressure (20.4+/-1.6, 50.7+/-3.3, 35.7+/-2.8 and 30.0+/-2.6 mm Hg, respectively). The decreases in heart rate in response to these concentrations of MCH were 40.0+/-8.7, 90.0+/-13.0, 48.0+/-7.3 and 48.0+/-8.0 beats/min, respectively. Maximum cardiovascular responses were elicited by a 0.5 mM concentration of MCH. Cardiovascular responses to MCH were similar in unanesthetized mid-collicular decerebrate rats. Control microinjections of normal saline (100 nl) did not elicit any cardiovascular response. Ipsilateral or bilateral vagotomy significantly attenuated MCH-induced bradycardia. Prior microinjections of PMC-3881-PI (2 mM; MCH-1 receptor antagonist) into the mNTS blocked the cardiovascular responses to microinjections of MCH. Microinjection of MCH (0.5 mM) into the mNTS decreased efferent greater splanchnic nerve activity. Direct application of MCH (0.5 mM; 4 nl) to barosensitive nucleus tractus solitarius (NTS) neurons increased their firing rate. These results indicate that: 1) MCH microinjections into the mNTS activate MCH-1 receptors and excite barosensitive NTS neurons, causing a decrease in efferent sympathetic activity and blood pressure, and 2) MCH-induced bradycardia is mediated via the activation of the vagus nerves.
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Affiliation(s)
- S N Brown
- Department of Neurological Surgery, MSB H-586, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103, USA
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