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Nunn N, Womack M, Dart C, Barrett-Jolley R. Function and pharmacology of spinally-projecting sympathetic pre-autonomic neurones in the paraventricular nucleus of the hypothalamus. Curr Neuropharmacol 2011; 9:262-77. [PMID: 22131936 PMCID: PMC3131718 DOI: 10.2174/157015911795596531] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 09/01/2010] [Accepted: 09/14/2010] [Indexed: 12/16/2022] Open
Abstract
The paraventricular nucleus (PVN) of the hypothalamus has been described as the "autonomic master controller". It co-ordinates critical physiological responses through control of the hypothalamic-pituitary-adrenal (HPA)-axis, and by modulation of the sympathetic and parasympathetic branches of the central nervous system. The PVN comprises several anatomical subdivisions, including the parvocellular/ mediocellular subdivision, which contains neurones projecting to the medulla and spinal cord. Consensus indicates that output from spinally-projecting sympathetic pre-autonomic neurones (SPANs) increases blood pressure and heart rate, and dysfunction of these neurones has been directly linked to elevated sympathetic activity during heart failure. The influence of spinally-projecting SPANs on cardiovascular function high-lights their potential as targets for future therapeutic drug development. Recent studies have demonstrated pharmacological control of these spinally-projecting SPANs with glutamate, GABA, nitric oxide, neuroactive steroids and a number of neuropeptides (including angiotensin, substance P, and corticotrophin-releasing factor). The underlying mechanism of control appears to be a state of tonic inhibition by GABA, which is then strengthened or relieved by the action of other modulators. The physiological function of spinally-projecting SPANs has been subject to some debate, and they may be involved in physiological stress responses, blood volume regulation, glucose regulation, thermoregulation and/or circadian rhythms. This review describes the pharmacology of PVN spinally-projecting SPANs and discusses their likely roles in cardiovascular control.
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Affiliation(s)
| | | | | | - Richard Barrett-Jolley
- Centre for Integrative Mammalian Biology, University of Liverpool, Brownlow Hill & Crown St. Liverpool, L69 7ZJ, UK
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Cloutier F, Lauschke JL, Carrive P. Compensatory mechanisms to maintain blood pressure in paraplegic rats: implication of central tachykinin NK-1 and NK-3 receptors? Neuropeptides 2010; 44:199-207. [PMID: 20096457 DOI: 10.1016/j.npep.2009.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 12/14/2009] [Accepted: 12/18/2009] [Indexed: 11/25/2022]
Abstract
People with high level spinal cord injury (SCI) suffer from both hypotension and spontaneous hypertension due to loss of supraspinal control of spinal sympathetic outflow. Few reports have addressed whether any changes occur in central regulation of blood pressure (BP) and heart rat (HR) at the supraspinal level. Central tachykinin NK-1 and NK-3 receptors are located in many cardiovascular areas in the brain and are known to modulate BP and HR. This study examined the intracerebroventricular (i.c.v.) effects of the selective NK-1 receptor agonist [Sar(9), Met(O(2))(11)]SP (65pmol, n=6) and NK-3 receptor agonist senktide (650pmol, n=6) on mean arterial pressure (MAP) and HR before and after complete spinal cord transection at thoracic level 4 (T4). [Sar(9), Met(O(2))(11)]SP evoked increases in MAP and HR which were still present 4days after the T4 SCI. Further analysis using the beta(1)-adrenoceptor antagonist atenolol (10mgkg(-1)) revealed an increased contribution of HR in the MAP increase after SCI. For senktide, 2 and 5weeks after T4 SCI, the rise in MAP induced by senktide was significantly increased in magnitude and was similar to a normal response at 8weeks. These effects were accompanied by a bradycardia, which was still present and amplified at 8weeks. Our results reveal a transient potentiation of the senktide-mediated MAP effect and a greater contribution of the HR in MAP increase by [Sar(9), Met(O(2))(11)]SP in T4 transected rats. Although the significance of these changes remains to be established. This suggest a reorganization of supraspinal mechanisms regulating BP and HR after a high level SCI. Central NK-1 and NK-3 receptors might therefore contribute to the maintenance of MAP following high thoracic SCI.
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Affiliation(s)
- Frank Cloutier
- Neural Injury Research Unit, School of Anatomy, University New South Wales Sydney, Australia.
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Womack MD, Morris R, Gent TC, Barrett-Jolley R. Substance P targets sympathetic control neurons in the paraventricular nucleus. Circ Res 2007; 100:1650-8. [PMID: 17495222 DOI: 10.1161/circresaha.107.153494] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The paraventricular nucleus (PVN) contains spinally-projecting neurons implicated in fine-tuning the cardiovascular system. In vivo activity of "presympathetic" parvocellular neurons is suppressed by tonic inhibition from GABA-ergic inputs, inhibition of which increases sympathetic pressor activity and heart rate. Targeting of this specific neuronal population could potentially limit elevations of heart rate and blood pressure associated with disease. Here we show, for the first time, that "presympathetic" PVN neurons are disinhibited by the neuropeptide substance P (SP) acting via tachykinin NK1 receptor inhibition of GABA(A) currents. Application of SP to the paraventricular nucleus of rats increases heart rate and blood pressure. In in vitro brain slice experiments, in the presence of GABA, 1 micromol/L SP increased action current frequency by a factor of 2.7+/-0.6 (n=5, P< or =0.05, ANOVA). Furthermore, 1 micromol/L SP inhibited GABA(A) currents by 70+/-8% (n=8, P< or =0.005 paired t test). These effects were abolished by NK1 antagonists, but not NK2 and NK3 antagonists. GABA(A) inhibition was not reproduced by NK2 or NK3 agonists. The inhibition of parvocellular GABA(A) currents by SP was also abolished by a protein kinase C (PKC) inhibitor peptide and mimicked by application of phorbol-12-myristate-13-acetate (PMA), implicating a PKC-dependent mechanism. Single-channel analysis indicates that SP acts through reduction of channel mean open-time (cmot): GABA(A) cmot being reduced by approximately 60% by SP (P< or =0.05 ANOVA, Bonferroni). These data suggest that tachykinins mediate their pressor activity by increasing the excitability of spinally-projecting neurons and identifies NK1 receptors as potential targets for therapeutic modulation of the cardiovascular system.
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Affiliation(s)
- Matthew D Womack
- Veterinary Sciences Faculty, Brownlow Hill, University of Liverpool, UK
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Womack MD, Barrett-Jolley R. Activation of paraventricular nucleus neurones by the dorsomedial hypothalamus via a tachykinin pathway in rats. Exp Physiol 2007; 92:671-6. [PMID: 17468202 DOI: 10.1113/expphysiol.2007.037457] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The dorsomedial hypothalamus (DMH) innervates the paraventricular nucleus (PVN) with substance P (SP) immunoreactive neurones. The PVN itself powerfully influences both the neuroendocrine and the cardiovascular systems. In this in vitro study, we examine the DMH-to-PVN pathway electrophysiologically. Glutamate application to the DMH increased action current frequency in the PVN. This effect was prevented by the glutamate antagonist kynurenic acid or by synaptic block with a high-Mg(2)(+) low-Ca(2)(+) buffer solution. Crucially, the selective tachykinin NK1 receptor antagonist L-703606 also inhibited DMH-to-PVN neurotransmission. Thus we show, for the first time, an excitatory connection between the DMH and PVN that uses tachykinin NK1 receptors. This pathway may be important for the hypothalamic control of neuroendocrine and/or cardiovascular function.
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Affiliation(s)
- Matthew D Womack
- Department of Veterinary Preclinical Sciences, Veterinary Sciences Building, Brownlow Hill & Crown Street, University of Liverpool, Liverpool L69 7ZJ, UK
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Abstract
Serotonin has been implicated in mediating the hypothalamo-pituitary-adrenal (HPA) axis response to stress and is an important therapeutic target for a number of psychiatric disorders including depression. The neurokinin substance P has been shown to inhibit stress-induced HPA axis activity and we have demonstrated that endogenous substance P is able to reduce the duration of the HPA axis response to stress suggesting an important role in the termination of the stress response. This may be important in controlling the transition from acute to chronic stress and substance P has recently attracted attention as a potential antidepressant.In addition to these central effects, serotonin and substance P are considered to be pro-inflammatory agents. Despite being implicated in mediating inflammation there have been few studies investigating the effects of manipulations of serotonergic or substance P systems on chronic inflammatory disease. Treatment of rats with adjuvant-induced arthritis(AA), a model of chronic inflammatory stress, with a substance P antagonist specific for the NK1 receptor subtype resulted in a reduction in hind paw inflammation suggesting substance P may influence inflammation. We have noted that depletion of whole body serotonin and selective central depletion of serotonin results in a decrease in the severity of inflammation in rats with adjuvant arthritis. Furthermore, treatment with a selective serotonin reuptake inhibitor results in an earlier onset and increased severity of inflammation in adjuvant arthritis, confirming a pro-inflammatory role for serotonin. Serotonin is also present in the immune tissues and concentrations in the spleen fall following the development of inflammation in adjuvant arthritis. Concentrations of serotonin are significantly higher in normal female spleen than in males, and this may underlie the greater predisposition of females to certain autoimmune diseases.There is increasing evidence of a role for transmitters such as serotonin and substance P,both centrally and peripherally, in mediating a wide variety of inflammatory and psychiatric disorders. A better understanding of the mechanisms of action of these transmitters and the development of suitable drugs targeting specific receptor subtypes has great potential to impact on clinical practice in the near future. The purpose of this review is to consider the separate roles of serotonin and substance P in relation to HPA axis stress responses, in the context of a model of chronic inflammatory disease, highlighting novel directions of current research for each of these transmitters.
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Affiliation(s)
- M S Harbuz
- URC Neuroendocrinology, University of Bristo1, BRI, Marlborough Street, Bristol BS2 8HW UK
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Bauman NM, Wang D, Sandler AD, Luschei ES. Response of the cricothyroid and thyroarytenoid muscles to stereotactic injection of substance P into the region of the nucleus tractus solitarius in developing dogs. Ann Otol Rhinol Laryngol 2000; 109:1150-6. [PMID: 11130829 DOI: 10.1177/000348940010901213] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Substance P (SP), a putative sensory neurotransmitter, mediates reflex laryngeal adductor activity in developing dogs. Such reflex activity includes life-threatening laryngospasm induced by stimulation of distal esophageal afferent nerves. The site of SP's activity is unknown. This research was undertaken to determine whether injection of SP into the nucleus tractus solitarius (NTS) of developing beagles alters laryngeal adductor motor activity. Six animals, 57 to 78 days of age, underwent stereotactic injection of 5 to 10 microL of SP into the region of the NTS, identified by electrical stimulation of the ipsilateral superior laryngeal nerve. In 8 additional studies, SP was injected into the cerebellum (2) or brain stem (6) distant from the NTS. Cardiovascular and electromyographic (EMG) responses of the diaphragm and the cricothyroid (CT) and/or thyroarytenoid (TA) muscles were recorded in all 6 animals. Injection of SP into the region of the NTS induced a decrease in blood pressure in all animals and an increase in either ipsilateral CT or TA activity. Three of these animals experienced mixed apnea characterized by sustained EMG activity (spasm) of the ipsilateral CT or TA muscles and an absence of diaphragm EMG activity. The apnea event was fatal in 1 of these animals. In the 6 animals who underwent injections in the brain stem but outside the region of the NTS, diaphragm and laryngeal EMG activity generally did not change after injection of SP, with the exception of 1 animal who experienced a mild, short-lived increase in ipsilateral CT activity. A brief phasic increase in ipsilateral CT activity was seen in both animals who underwent injection of SP into the cerebellum. A putative sensory neurotransmitter, SP evokes ipsilateral CT and/or TA EMG activity when injected into the region of the NTS in developing beagle dogs. This research suggests that SP in the NTS may play a role in mediating life-threatening laryngeal adductor reflexes in developing mammals and may provide important information regarding therapeutic intervention.
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Affiliation(s)
- N M Bauman
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City 52242, USA
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Abstract
UNLABELLED Empirical efforts to prove or disprove an association between stress and the course of inflammatory bowel disease (IBD) have had inconsistent results. Direct study of mediators of stress-related physiological processes may clarify this important area. METHODS candidate mediators were selected based on evidence that they have a role in the pathophysiology of IBD. Medline searches for original articles addressing each putative mediator and psychological stress were conducted. Articles were reviewed with goals of synthesis and hypothesis generation. RESULTS there is evidence that substance P (SP), vasoactive intestinal protein (VIP), tumour necrosis factor alpha (TNFalpha), oxidant molecules, endogenous glucocorticoids and heat shock proteins (HSPs) are involved in the stress response. DISCUSSION two principles emerge which should inform efforts to investigate stress in IBD. First, stress effects are regulated by highly interdependent systems. Second, the effects of mediators are highly specific to the location of their activity, and so, investigations in IBD are likely to require direct investigation of inflamed and unaffected gut tissue.
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Affiliation(s)
- R Maunder
- Department of Psychiatry, Mount Sinai Hospital and University of Toronto, 9th Floor, 600 University Ave., Toronto, Ontario, Canada.
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Jessop DS, Renshaw D, Larsen PJ, Chowdrey HS, Harbuz MS. Substance P is involved in terminating the hypothalamo- pituitary-adrenal axis response to acute stress through centrally located neurokinin-1 receptors. Stress 2000; 3:209-20. [PMID: 10938582 DOI: 10.3109/10253890009001125] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The neurokinin substance P (SP) has been previously shown to inhibit basal hypothalamo-pituitary-adrenal (HPA) axis activity. This study was designed to investigate the effects of central injection of the specific neurokinin-1 receptor antagonist RP67580 on the HPA axis response to acute restraint stress. In non-restrained rats injected with RP67580, plasma ACTH and corticosterone levels were elevated at 30 and 60 min compared to rats injected with vehicle, but there were no differences between vehicle and RP67580 groups at 4h. In restrained rats injected with vehicle, plasma ACTH and corticosterone levels were significantly elevated at 30 min and 60 min following initiation of the stress but had returned to basal levels at 4h. In restrained rats injected icv with RP67580, plasma corticosterone and ACTH levels were significantly elevated at 30 min and 60 min, with no significant differences compared to the restraint stressed vehicle-injected group. However, in the RP67580-injected group, corticosterone and ACTH levels remained significantly elevated at 4h following onset of restraint compared to those in the restraint stressed vehicle-injected group. Corticotrophin-releasing factor mRNA levels in the parvocellular subdivision of the paraventricular nucleus of the hypothalamus and POMC mRNA levels in the anterior pituitary were significantly increased in the stressed group 4h following injection with RP67580 compared to the stressed group injected with vehicle alone. These data show that endogenous SP does not inhibit the initial magnitude of the HPA axis response to restraint stress, but does act through neurokinin-1 receptors at a central level to reduce the duration of the response to stress. This suggests that SP may be an important central agent controlling the transition between acute and chronic stress.
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Affiliation(s)
- D S Jessop
- Division of Medicine, University of Bristol, Bristol, U.K.
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Bauman NM, Wang D, Jaffe DM, Sandler AD, Luschei ES. Effect of intravenous substance P on laryngeal adductor activity in young dogs. Ann Otol Rhinol Laryngol 1999; 108:112-8. [PMID: 10030226 DOI: 10.1177/000348949910800202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Reflex laryngeal adduction is a component of both the laryngeal chemoreflex and the esophagolaryngeal adductor reflex, two life-threatening reflexes that occur in immature animals. These two reflex responses are also thought to exist in infants and may play a role in causing life-threatening laryngospastic events and perhaps sudden infant death syndrome. Identifying neurotransmitters that mediate laryngeal adduction is important to understanding the mechanism of reflex laryngeal responses and to identifying potential means of pharmacologic prevention. Substance P (SP), a tachykinin, putatively functions as a sensory neurotransmitter and may play a role in mediating laryngeal reflexes. Substance P-immunoreactive-like fibers and receptors are present in the subepithelial tissues of the larynx, the vagus nerves, the nodose and jugular ganglia, and the vagal brain stem nuclei. In this investigation, the effect of SP infusion on laryngeal motor activity in an in vivo model is reported. Substance P was infused intravenously into 8 puppies (20 to 133 days of age, mean 81.2), on a mean of 3.0 occasions (range 1 to 6). Cardiovascular, respiratory, arterial blood gas, and cricothyroid (CT), thyroarytenoid (TA), and genioglossus electromyographic (EMG) responses to infusion of the tachykinin were recorded and subsequently analyzed. The SP infusion induced a marked increase in CT or TA EMG activity in 23 of 24 studies, and the increase was typically apparent within 60 seconds of the infusion. An increase in genioglossus EMG activity did not occur. An immediate, profound decrease in mean arterial pressure and an increase in respiratory rate and depth of chest wall excursion accompanied the laryngeal response. Arterial blood gas values remained unchanged (p > .05). The laryngeal adductor response to SP infusion was blocked when animals were pretreated with a systemic SP antagonist (Pfizer CP-96,345). This study demonstrates that peripheral infusion of the tachykinin SP induces a marked increase in laryngeal adductor activity. The response may be blocked by pretreatment of animals with a systemic SP antagonist. Because SP is thought to act primarily as a sensory neurotransmitter, these findings may be important in understanding the mechanism of reflex laryngeal adductor responses.
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Affiliation(s)
- N M Bauman
- Department of Otolaryngology-Head and Neck Surgery, The University of Iowa College of Medicine, Iowa City, USA
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Hahn MK, Bannon MJ. Tachykinin NK1 receptor antagonists enhance stress-induced c-fos in rat locus coeruleus. Eur J Pharmacol 1998; 348:155-60. [PMID: 9652329 DOI: 10.1016/s0014-2999(98)00150-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
These experiments tested the hypothesis that substance P neurotransmission at tachykinin NK1 receptors in the locus coeruleus is involved in stress-induced activation of the locus coeruleus, using c-fos as an index of activation. Selective tachykinin NK1 receptor antagonists administered systemically did not result in substantial locus coeruleus c-fos expression. Restraint stress resulted in a large number of locus coeruleus c-fos expressing cells. Administration of two selective tachykinin NK1 receptor antagonists prior to restraint resulted in an increase in the number of locus coeruleus c-fos expressing cells, compared to restraint alone. These results suggest that the enhanced c-fos expression observed in response to tachykinin NK1 receptor antagonists combined with stress, could be due to the blockade of tachykinin NK1 receptor-mediated activity at sites other than the locus coeruleus, resulting in an overall activation of the locus coeruleus.
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Affiliation(s)
- M K Hahn
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University Medical School, Detroit, MI 48201, USA
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