α2AAdrenoceptors Contribute to Feedback Inhibition of Capsaicin-induced Hyperalgesia

2004 ◽  
Vol 101 (1) ◽  
pp. 185-190 ◽  
Author(s):  
Heikki Mansikka ◽  
Janne Lähdesmäki ◽  
Mika Scheinin ◽  
Antti Pertovaara
Keyword(s):  
Knockout Mice ◽  
Feedback Inhibition ◽  
Pain Behavior ◽  
Spontaneous Pain ◽  
Wild Type ◽  
Pain Hypersensitivity ◽  
Adrenoceptor Antagonist ◽  
Adrenoceptor Agonist ◽  
Adrenoceptor Agonists ◽  
Alpha2 Adrenoceptor

Background Studies on receptor knockout mice have so far shown that of the three alpha2-adrenoceptor subtypes, the alpha(2A) adrenoceptor has a major role in mediating the powerful central analgesia induced by synthetic alpha2-adrenoceptor agonists. However, because a knockout of the gene for the alpha(2A) adrenoceptor has produced only little if any change in the pain sensitivity of control, nerve-injured, or inflamed animals, it has not been clear whether activation of alpha(2A)-adrenoceptors by endogenous ligands has a significant pain regulatory role. Methods The authors assessed spontaneous pain behavior and mechanical hypersensitivity induced by administration of capsaicin in the colon or paw of alpha(2A)-adrenoceptor knockout mice versus their wild-type controls. Results Enhanced pain hypersensitivity was observed in alpha(2A)-adrenoceptor knockout mice 20 min or more after administration of capsaicin, but before, hypersensitivity and spontaneous pain were of equal magnitude in alpha(2A)-adrenoceptor knockout and wild-type mice. When wild-type mice were pretreated with an alpha2-adrenoceptor antagonist, capsaicin-induced pain hypersensitivity increased to a level equal to that in alpha(2A)-adrenoceptor knockout mice. Capsaicin-induced hypersensitivity was suppressed in wild-type but not alpha(2A)-adrenoceptor knockout mice by a centrally acting alpha2-adrenoceptor agonist, whereas a peripherally acting alpha2-adrenoceptor agonist was without effect on hypersensitivity, although it attenuated capsaicin-induced spontaneous pain behavior in wild-type mice. Conclusions This study shows that central alpha(2A)-adrenoceptors contribute to feedback inhibition of pain hypersensitivity. Also, alpha(2A)-adrenoceptors are critical for not only somatic but also visceral antinociceptive effects induced by synthetic alpha2-adrenoceptor agonists.

The Effect of Imidazoline Receptors and α2-adrenoceptors on the Anesthetic Requirement (MAC) for Halothane in Rats 

1997 ◽  
Vol 87 (4) ◽  
pp. 963-967 ◽  
Author(s):  
Kiyokazu Kagawa ◽  
Tadanori Mammoto ◽  
Yukio Hayashi ◽  
Takahiko Kamibayashi ◽  
Takashi Mashimo ◽  
...  
Keyword(s):  
Minimum Alveolar Concentration ◽  
Inhibitory Effect ◽  
Imidazoline Receptors ◽  
Adrenoceptor Antagonist ◽  
Adrenoceptor Agonist ◽  
Adrenoceptor Agonists ◽  
The Central Nervous System ◽  
Anesthetic Requirement ◽  
Alpha2 Adrenoceptor ◽  
Pharmacologic Actions

Background Recent evidences have documented that several pharmacologic actions of alpha2-adrenoceptor agonists are mediated via activation of not only alpha2-adrenoceptors, but also by imidazoline receptors, which are nonadrenergic receptors in the central nervous system. However, the effect of imidazoline receptors on the anesthesia is not well known, and it is important to clarify the effects of both receptors on anesthesia. Methods Seventy-two rats were anesthetized with halothane, and the anesthetic requirement for halothane was evaluated as minimum alveolar concentration (MAC). The MAC for halothane was determined in the presence of dexmedetomidine (0, 10, 20, and 30 microg/kg, intraperitoneally [IP]), a selective alpha2-adrenoceptor agonist with weak affinity for imidazoline receptors. Then, the authors evaluated the inhibitory effect of rauwolscine (20 mg/kg, IP), an alpha2-adrenoceptor antagonist with little affinity for imidazoline receptors, on the MAC-reducing action of dexmedetomidine (30 microg/kg). Further, the effect of rilmenidine (20, 50, 100, 1000 microg/kg, IP), a selective imidazoline receptor agonist, on the MAC for halothane was also investigated. Results Dexmedetomidine decreased the MAC for halothane dose-dependently, and this MAC-reducing action of dexmedetomidine was completely blocked by rauwolscine. Rilmenidine alone did not change the MAC for halothane. Conclusions The present data indicate that the anesthetic sparing action of dexmedetomidine is most likely mediated through alpha2- adrenoceptors, and the stimulation of imidazoline receptors exerts little effect on the anesthetic requirement for halothane.

Effects of α-adrenoceptor agonists and antagonists on thyroid hormone secretion

1985 ◽  
Vol 108 (2) ◽  
pp. 184-191 ◽  
Author(s):  
Bo Ahrén
Keyword(s):  
Thyroid Hormone ◽  
Dose Level ◽  
Hormone Secretion ◽  
High Dose ◽  
Inhibitory Effects ◽  
High Dose Level ◽  
Adrenoceptor Antagonist ◽  
Adrenoceptor Agonist ◽  
Adrenoceptor Agonists

Abstract. The effects of various α-adrenoceptor agonists and antagonists on blood radioiodine levels were studied in mice pre-treated with 125I and thyroxine. The non-selective α-adrenoceptor agonist noradrenaline and the selective α1-adrenoceptor agonist phenylephrine both enhanced blood radioiodine levels. Noradrenaline was more potent than phenylephrine. Contrary, the selective α2-adrenoceptor agonist clonidine depressed basal levels of blood radioiodine. The non-selective α-adrenoceptor antagonist phentolamine and the selective α1-adrenoceptor antagonist prazosin both inhibited the noradrenaline-induced elevation of radioiodine levels, whereas the α2-adrenoceptor antagonist yohimbine had no such effect, except at a high dose level. All three α-adrenoceptor agonists, noradrenaline, phenylephrine and clonidine, inhibited the radioiodine response to TSH. In addition, TSH-induced increase in radioiodine levels was inhibited by prazosin, whereas yohimbine had no effect. Phentolamine inhibited the radioiodine response to TSH when given 2 h prior to TSH, whereas when given 15 min prior to TSH the response to TSH was potentiated by Phentolamine. It is concluded, that under in vivo conditions in the mouse, α1-adrenoceptor activation stimulates basal thyroid hormone secretion and inhibits TSH-induced thyroid hormone secretion. Further, α2-adrenoceptor activation inhibits basal thyroid hormone secretion. In addition, TSH-induced thyroid hormone secretion is inhibited by α1-adrenoceptor antagonism. Thus, α-adrenoceptors induce both stimulatory and inhibitory effects of thyroid function.

scholarly journals Catecholamines modulate podocyte function.

1998 ◽  
Vol 9 (3) ◽  
pp. 335-345 ◽  
Author(s):  
T B Huber ◽  
J Gloy ◽  
A Henger ◽  
P Schollmeyer ◽  
R Greger ◽  
...  
Keyword(s):  
Channel Blocker ◽  
Patch Clamp Technique ◽  
Extracellular Solution ◽  
Adrenoceptor Antagonist ◽  
Adrenoceptor Agonist ◽  
Adrenoceptor Agonists ◽  
Beta 2 ◽  
Cl Conductance ◽  
Stimulation Of ◽  
Ion Conductances

The aim of this study was to investigate the influence of adrenoceptor agonists on the intracellular calcium activity ([Ca2+]i), membrane voltage (Vm), and ion conductances (Gm) in differentiated mouse podocytes. [Ca2+]i was measured by the Fura-2 fluorescence method in single podocytes. Noradrenaline and the alpha 1-adrenoceptor agonist phenylephrine induced a reversible and concentration-dependent biphasic increase of [Ca2+]i in podocytes (EC50 approximately 0.1 microM for peak and plateau), whereas the alpha 2-adrenoceptor agonist UK 14.304 did not influence [Ca2+]i. The [Ca2+]i response induced by noradrenaline was completely inhibited by the alpha 1-adrenoceptor antagonist prazosin (10 nM). In a solution with a high extracellular K+ (72.5 mM), [Ca2+]i was unchanged and the [Ca2+]i increase induced by noradrenaline was not inhibited by the L-type Ca2+ channel blocker nicardipine (1 microM). Vm and Gm were examined with the patch-clamp technique in the slow whole-cell configuration. Isoproterenol, phenylephrine, and noradrenaline depolarized podocytes and increased Gm. The order of potency for the adrenoceptor agonists was isoproterenol (EC50 approximately 1 nM) > noradrenaline (EC50 approximately 0.3 microM) > phenylephrine (EC50 approximately 0.5 microM). The beta 2-adrenoceptor antagonist ICI 118.551 (5 to 100 nM) inhibited the effect of isoproterenol on Vm. Stimulation of adenylate cyclase by forskolin mimicked the effect of isoproterenol on Vm and Gm (EC50 approximately 40 nM). Isoproterenol induced a time- and concentration-dependent increase of cAMP in podocytes. The effect of isoproterenol was unchanged in the absence of Na+ or in an extracellular solution with a reduced Ca2+ concentration, whereas it was significantly increased in an extracellular solution with a reduced Cl- concentration (from 145 to 32 mM). The data indicate that adrenoceptor agonists regulate podocyte function: They increase [Ca2+]i via an alpha 1-adrenoceptor and induce a depolarization via a beta 2-adrenoceptor. The depolarization is probably due to an opening of a cAMP-dependent Cl- conductance.

Central catecholaminergic neurons are involved in expression of the 10-Hz rhythm in SND

1996 ◽  
Vol 270 (2) ◽  
pp. R333-R341 ◽  
Author(s):  
H. S. Orer ◽  
S. Zhong ◽  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Intravenous Administration ◽  
Sympathetic Nerve ◽  
Ventrolateral Medulla ◽  
Imidazoline Receptors ◽  
Catecholaminergic Neurons ◽  
Adrenoceptor Antagonist ◽  
Adrenoceptor Agonist ◽  
Adrenoceptor Agonists ◽  
Nerve Discharge ◽  
Lower Frequencies

We studied the effects of adrenoceptor agonists and antagonists on sympathetic nerve discharge (SND) of urethan-anesthetized, baroreceptor-denervated cats. In cats in which a 10-Hz rhythm coexisted with irregular 2- to 6-Hz oscillations in SND, intravenous clonidine, an alpha 2-adrenoceptor agonist, blocked the 10-Hz rhythm without affecting power at lower frequencies. In contrast, power at frequencies < or = 6 Hz was depressed by clonidine in cats in which the 10-Hz rhythm was absent. These effects were reversed by intravenous administration of alpha 2-adrenoceptor antagonists, idazoxan and rauwolscine. Rauwolscine is devoid of affinity for imidazoline receptors. Furthermore, in cats untreated with clonidine, idazoxan and rauwolscine enhanced or induced the 10-Hz rhythm without affecting power at lower frequencies. Prazosin, an alpha 1-adrenoceptor antagonist, selectively blocked the 10-Hz rhythm in SND. Finally, the 10-Hz rhythm in SND was blocked by microinjection of clonidine into the rostral or caudal ventrolateral medulla. The results support the view that central catecholaminergic neurons play a role in expression of the 10-Hz rhythm in SND.

scholarly journals Various Systemic Effects of MK-467, A Peripherally Acting α2-adrenoceptor Antagonist in Different Animal Species: An Overview

2020 ◽  
Author(s):  
Akash . ◽  
M. Hoque ◽  
Amarpal .
Keyword(s):  
Animal Species ◽  
Minimum Alveolar Concentration ◽  
Cardiovascular Effects ◽  
Concomitant Administration ◽  
Plasma Drug ◽  
Adrenoceptor Antagonist ◽  
Α2 Adrenoceptor ◽  
Adrenoceptor Agonist ◽  
Adrenoceptor Agonists ◽  
Cardiopulmonary System

Most commonly used α2-adrenoceptor agonist shows adverse cardiovascular effects during anaesthesia. They mainly depress the cardiovascular system by provoking vasoconstriction followed by bradycardia. Although α2-adrenoceptor antagonist like atipamezole can reverse these effects along with that they also reverse the sedation and nociception. Concomitant administration of peripherally acting α2-adrenoceptor antagonist MK-467 can reverse the adverse cardiovascular effect of α2-adrenoceptor agonists without affecting the sedation and nociception. MK-467 has been successfully used in different animals like dogs, cats, sheep, horses along with different α2-adrenoceptor agonist drugs. This review aims to summarize the effects of MK-467 on sedation, cardiopulmonary system, the minimum alveolar concentration of different inhalant anaesthetics, plasma drug concentration, plasma glucose and insulin in different animals.

β2-Adrenoceptor Regulation of CGRP Release from Capsaicin-sensitive Neurons

2003 ◽  
Vol 82 (4) ◽  
pp. 308-311 ◽  
Author(s):  
W.R. Bowles ◽  
C.M. Flores ◽  
D.L. Jackson ◽  
K.M. Hargreaves
Keyword(s):  
Dental Pulp ◽  
Nociceptive Neurons ◽  
Adrenoceptor Antagonist ◽  
Adrenoceptor Agonist ◽  
In Vitro Superfusion ◽  
Adrenoceptor Agonists ◽  
Adrenoceptor Regulation ◽  
Pre Treatment ◽  
Neurotransmitter Substances

Previous studies have suggested that neurotransmitter substances from the sympatho-adrenomedullary system regulate pulpal blood flow (PBF), in part, by the inhibition of vasoactive neuropeptide release from pulpal sensory neurons. However, no study has evaluated the role of β-adrenoceptors. We evaluated the hypothesis that activation of β-adrenoceptors inhibits immunoreactive calcitonin gene-related peptide (iCGRP) release from capsaicin-sensitive nociceptive neurons via in vitro superfusion of bovine dental pulp. Either norepinephrine or epinephrine inhibited capsaicin-evoked iCGRP. The norepinephrine effect was blocked by the selective β2-adrenoceptor antagonist, ICI 118,551, but not by pre-treatment with the selective β1-adrenoceptor antagonist, atenolol. In addition, application of albuterol, a selective β2-adrenoceptor agonist, significantly blocked capsaicin-evoked release of iCGRP. Collectively, these studies demonstrate that activation of β2-adrenoceptors in dental pulp significantly reduces exocytosis of neuropeptides from capsaicin-sensitive nociceptors. This effect may have physiologic significance in regulating PBF. Moreover, since capsaicin selectively activates nociceptors, β2-adrenoceptor agonists may have clinical utility as peripherally acting therapeutics for dental pain and inflammation.

Attenuation of Ascending Nociceptive Signals to the Rostroventromedial Medulla Induced by a Novel α2-Adrenoceptor Agonist, MPV-2426, following Intrathecal Application in Neuropathic Rats

2000 ◽  
Vol 92 (4) ◽  
pp. 1082-1092 ◽  
Author(s):  
Antti Pertovaara ◽  
Hong Wei
Keyword(s):  
Antinociceptive Effect ◽  
Intrathecal Administration ◽  
Systemic Administration ◽  
The Body ◽  
Mechanical Stimuli ◽  
Nociceptive Neurons ◽  
Adrenoceptor Antagonist ◽  
Test Stimulation ◽  
Adrenoceptor Agonist ◽  
Alpha2 Adrenoceptor

Background In the current study, the potency and spread of the antinociception induced by MPV-2426, a novel alpha2-adrenoceptor agonist, was characterized in neuropathic and non-neuropathic animals. Methods Neuropathy was induced by unilateral ligation of two spinal nerves in the rat. After lumbar intrathecal or systemic administration of MPV-2426, thermally and mechanically evoked responses of nociceptive neurons of the rostroventromedial medulla were recorded during pentobarbitone anesthesia. To obtain a behavioral correlate of neurophysiologic findings, nocifensor reflex responses evoked by thermal and mechanical stimuli were assessed in unanesthetized neuropathic and control animals. Results After intrathecal administration, MPV-2426 and dexmedetomidine produced a dose-related antinociceptive effect, independent of the submodality of the noxious test stimulus or the pathophysiologic condition. This antinociceptive effect was spatially restricted to the inputs from the lower half of the body, and it was reversed by atipamezole, an alpha2-adrenoceptor antagonist. After systemic administration in non-neuropathic animals, MPV-2426 had no antinociceptive effect on responses to rostroventromedial medulla neurons, whereas systemically administered dexmedetomidine produced a dose-related suppression of nociceptive signals to the rostroventromedial medulla, independent of the site of test stimulation. In a behavioral study, intrathecal MPV-2426 produced a dose-dependent suppression of nocifensor responses evoked by noxious mechanical or heat stimuli, whereas systemic administration of MPV-2426 had no effects. Conclusions Intrathecal MPV-2426 has spatially limited antinociceptive properties in neuropathic and non-neuropathic conditions because of its action on spinal alpha2-adrenoceptors. These properties may be advantageous when designing therapy for spatially restricted pain problems.

Sympathomimetic Drugs Stimulate the Output of Secretory Glycoproteins from Human Bronchi In Vitro

1982 ◽  
Vol 63 (1) ◽  
pp. 23-28 ◽  
Author(s):  
R. J. Phipps ◽  
I. P. Williams ◽  
P. S. Richardson ◽  
J. Pell ◽  
R. J. Pack ◽  
...  
Keyword(s):  
Secretory Cells ◽  
Ussing Chambers ◽  
Adrenoceptor Antagonist ◽  
Adrenoceptor Agonist ◽  
Sympathomimetic Drugs ◽  
Adrenoceptor Agonists ◽  
Secretory Glycoproteins ◽  
Glycoprotein Secretion ◽  
Human Bronchi

1. We describe a method for supporting pieces of human bronchi in Ussing chambers, for radiolabelling the contents of the secretory cells with 35S, and for collecting radiolabeled macromolecules secreted on to the luminal aspect of the tissue. This method has previously been used to study airway secretions in animals [R. J. Phipps, J. A. Nadel & B. Davis, American Review of Respiratory Disease, (1980) 121, 359–365]. Evidence is given that the radiolabelled molecules are secretory glycoproteins, probably mucus glycoproteins. 2. Phenylephrine, an α-adrenoceptor agonist, increased the rate at which the bronchi secreted radiolabeled glycoproteins. Thymoxamine, an α-adrenoceptor antagonist, blocked this effect but propranolol, a β-adrenoceptor antagonist, did not. 3. Dobutamine, a β1-adrenoceptor agonist, increased the rate of secretion of radiolabeled glycoproteins. Propranolol blocked this but thymoxamine did not. 4. Salbutamol, a β2-adrenoceptor agonist, also increased the rate of secretion of radiolabeled glycoproteins. Propranolol blocked this effect. 5. We conclude that both α and β-adrenoceptor agonists increase the rate of glycoprotein secretion in human bronchi in vitro and that this almost certainly means that they increase the rate of mucus secretion.

scholarly journals IL-17F depletion accelerates chitosan conduit guided peripheral nerve regeneration

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Feixiang Chen ◽  
Weihuang Liu ◽  
Qiang Zhang ◽  
Ping Wu ◽  
Ao Xiao ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Sciatic Nerve ◽  
Peripheral Nerve ◽  
Nerve Regeneration ◽  
Knockout Mice ◽  
Inflammatory Markers ◽  
Nerve Repair ◽  
Peripheral Nerve Regeneration ◽  
Wild Type ◽  
Anti Inflammatory

AbstractPeripheral nerve injury is a serious health problem and repairing long nerve deficits remains a clinical challenge nowadays. Nerve guidance conduit (NGC) serves as the most promising alternative therapy strategy to autografts but its repairing efficiency needs improvement. In this study, we investigated whether modulating the immune microenvironment by Interleukin-17F (IL-17F) could promote NGC mediated peripheral nerve repair. Chitosan conduits were used to bridge sciatic nerve defect in IL-17F knockout mice and wild-type mice with autografts as controls. Our data revealed that IL-17F knockout mice had improved functional recovery and axonal regeneration of sciatic nerve bridged by chitosan conduits comparing to the wild-type mice. Notably, IL-17F knockout mice had enhanced anti-inflammatory macrophages in the NGC repairing microenvironment. In vitro data revealed that IL-17F knockout peritoneal and bone marrow derived macrophages had increased anti-inflammatory markers after treatment with the extracts from chitosan conduits, while higher pro-inflammatory markers were detected in the Raw264.7 macrophage cell line, wild-type peritoneal and bone marrow derived macrophages after the same treatment. The biased anti-inflammatory phenotype of macrophages by IL-17F knockout probably contributed to the improved chitosan conduit guided sciatic nerve regeneration. Additionally, IL-17F could enhance pro-inflammatory factors production in Raw264.7 cells and wild-type peritoneal macrophages. Altogether, IL-17F may partially mediate chitosan conduit induced pro-inflammatory polarization of macrophages during nerve repair. These results not only revealed a role of IL-17F in macrophage function, but also provided a unique and promising target, IL-17F, to modulate the microenvironment and enhance the peripheral nerve regeneration.

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