1
|
Rivera-Mancilla E, Villanueva-Castillo B, Altamirano-Espinoza AH, Manrique-Maldonado G, Villalón CM. Prospective role of α2A/2B/2C-adrenoceptor subtypes in the modulation of cardioaccelerator sympathetic tone in an experimental model of diabetes. Eur J Pharmacol 2022; 929:175138. [DOI: 10.1016/j.ejphar.2022.175138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/28/2022] [Accepted: 06/30/2022] [Indexed: 11/15/2022]
|
2
|
The role of purinergic P2Y 12 and P2Y 13 receptors in ADPβS-induced inhibition of the cardioaccelerator sympathetic drive in pithed rats. Purinergic Signal 2020; 16:73-84. [PMID: 32067141 DOI: 10.1007/s11302-020-09689-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 01/23/2020] [Indexed: 11/27/2022] Open
Abstract
ATP is a cotransmitter released with other neurotransmitters from sympathetic nerves, where it stimulates purinergic receptors. Purinergic adenosine P1 receptors (coupled to Gi/o proteins) produce sympatho-inhibition in several autonomic effectors by prejunctional inhibition of neurotransmitter release. Similarly, signalling through P2Y12 and P2Y13 receptors coupled to Gi/o proteins is initiated by the ATP breakdown product ADP. Hence, this study has pharmacologically investigated a possible role of ADP-induced inhibition of the cardioaccelerator sympathetic drive in pithed rats, using a stable ADP analogue (ADPβS) and selective antagonists for the purinergic P2Y1, P2Y12 and P2Y13 receptors. Accordingly, male Wistar rats were pithed and: (i) pretreated i.v. with gallamine (25 mg/kg) and desipramine (50 μg/kg) for preganglionic spinal (C7-T1) stimulation of the cardioaccelerator sympathetic drive (n = 78); or (ii) prepared for receiving i.v. injections of exogenous noradrenaline (n = 12). The i.v. continuous infusions of ADPβS (10 and 30 μg/kg/min) dose-dependently inhibited the tachycardic responses to electrical sympathetic stimulation, but not those to exogenous noradrenaline. The cardiac sympatho-inhibition produced by 30 μg/kg/min ADPβS was (after i.v. administration of compounds) (i) unchanged by 1-ml/kg bidistilled water or 300-μg/kg MRS 2500 (P2Y1 receptor antagonist), (ii) abolished by 300-μg/kg PSB 0739 (P2Y12 receptor antagonist) and (iii) partially blocked by 3000-μg/kg MRS 2211 (P2Y13 receptor antagonist). Our results suggest that ADPβS induces a cardiac sympatho-inhibition that mainly involves the P2Y12 receptor subtype and, probably to a lesser extent, the P2Y13 receptor subtype. These receptors may represent therapeutic targets for treating cardiovascular pathologies, including stroke and myocardial infarctions.
Collapse
|
3
|
Rivera-Mancilla E, Altamirano-Espinoza AH, Manrique-Maldonado G, Villanueva-Castillo B, Villalón CM. Differential cardiac sympatho-inhibitory responses produced by the agonists B-HT 933, quinpirole and immepip in normoglycaemic and diabetic pithed rats. Clin Exp Pharmacol Physiol 2018; 45:767-778. [PMID: 29675928 DOI: 10.1111/1440-1681.12949] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 03/22/2018] [Accepted: 04/10/2018] [Indexed: 01/24/2023]
Abstract
This study compared the cardiac sympatho-inhibitory responses produced by agonists at α2 -adrenergic (B-HT 933), dopamine D2 -like (quinpirole) and histamine H3 /H4 (immepip) receptors between normoglycaemic and streptozotocin-pretreated (diabetic) pithed rats. Intravenous (i.v.) continuous infusions of B-HT 933, quinpirole or immepip were used in normoglycaemic and diabetic pithed rats to analyse their sympatho-inhibitory effects on the electrically-stimulated cardioaccelerator sympathetic outflow. Both in normoglycaemic and diabetic animals, B-HT 933 (until 100 μg/kg per minute) and quinpirole (until 10 μg/kg per minute) inhibited the tachycardic responses to electrical sympathetic stimulation, but not those to i.v. bolus of exogenous noradrenaline. These sympatho-inhibitory responses were more pronounced in diabetic than in normoglycaemic animals. Accordingly, the areas under the curve for 100 μg/kg per minute B-HT 933 and 10 μg/kg per minute quinpirole in diabetic rats (1065 ± 70 and 920 ± 35, respectively) were significantly smaller (P < .05) than those in normoglycaemic rats (1220 ± 45 and 1360 ± 42, respectively). In contrast, immepip infusions produced cardiac sympatho-inhibition in normoglycaemic (until 10 μg/kg per minute), but not in diabetic (until 100 μg/kg per minute) animals. Our results suggest that in diabetic pithed rats: (i) the more pronounced cardiac sympatho-inhibition to B-HT 933 and quinpirole may be probably due to up-regulation of α2 -adrenergic and dopamine D2 -like receptors, respectively; (ii) the histamine H3 /H4 receptors do not seem to play a sympatho-inhibitory role; and (iii) there is a differential participation of α2 -adrenergic and dopamine D2 -like receptors, which may certainly represent therapeutic targets for the treatment of diabetic complications such as cardiovascular autonomic neuropathy.
Collapse
|
4
|
Centurión D, de la Cruz SH, Castillo-Santiago SV, Becerril-Chacón ME, Torres-Pérez JA, Sánchez-López A. NaHS prejunctionally inhibits the cardioaccelerator sympathetic outflow in pithed rats. Eur J Pharmacol 2018; 823:35-40. [DOI: 10.1016/j.ejphar.2018.01.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 01/16/2018] [Accepted: 01/23/2018] [Indexed: 01/08/2023]
|
5
|
Cobos-Puc L, Aguayo-Morales H, Ventura-Sobrevilla J, Luque-Contreras D, Chin-Chan M. Further analysis of the inhibition by agmatine on the cardiac sympathetic outflow: Role of the α 2-adrenoceptor subtypes. Eur J Pharmacol 2017; 805:75-83. [PMID: 28315344 DOI: 10.1016/j.ejphar.2017.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 02/16/2017] [Accepted: 03/10/2017] [Indexed: 11/28/2022]
Abstract
This study has investigated the role of the α2-adrenoceptor subtypes involved in the inhibition of the cardiac sympathetic outflow induced by intravenous (i.v) infusions of agmatine. Therefore, we analysed the effect of an i.v. bolus injections of the selective antagonists BRL 44408 (300μg/kg; α2A), imiloxan (3000μg/kg; α2B), and JP-1302 (300μg/kg; α2C) given separately, and their combinations: BRL 44408 plus Imiloxan, JP 1302 plus imiloxan, BRL 44408 plus JP-1302, BRL 44408 plus imiloxan plus JP-1302 on the cardiac sympatho-inhibition of agmatine. Also, the effect of the combination BRL 44408 plus JP-1302 plus AGN 192403 (3000μg/kg; I1 antagonist) was evaluated. In this way, i.v. infusions of 1000μg/kg min of agmatine, but not 300, inhibited the tachycardic response induced by electrical stimulation. Furthermore, the antagonists used or their combinations had no effect on the electrically-induced tachycardic response. On the other hand, the inhibitory response of agmatine was: (1) partially antagonized by BRL 44408 or JP-1302 given separately, a similar response was observed when we administered their combination with imiloxan, but not by imiloxan alone, (2) antagonized in greater magnitude by the combination BRL 44408 plus JP-1302 or the combination BRL 44408 plus imiloxan plus JP-1302, and (3) abolished by the combination BRL 44408 plus JP-1302 plus AGN 192403. Taken together, these results demonstrate that the α2A- and α2C-adrenoceptor subtypes and I1-imidazoline receptors are involved in the inhibition of the cardiac sympathetic outflow induced by agmatine.
Collapse
Affiliation(s)
- Luis Cobos-Puc
- Facultad de Ciencias Químicas, Universidad Autónoma de Coahuila, Boulevard Venustiano Carranza esquina con Ing. José Cárdenas Valdés, Colonia República, C.P. 25280 Saltillo, Coahuila, Mexico.
| | - Hilda Aguayo-Morales
- Facultad de Ciencias Químicas, Universidad Autónoma de Coahuila, Boulevard Venustiano Carranza esquina con Ing. José Cárdenas Valdés, Colonia República, C.P. 25280 Saltillo, Coahuila, Mexico
| | - Janeth Ventura-Sobrevilla
- Facultad de Ciencias Químicas, Universidad Autónoma de Coahuila, Boulevard Venustiano Carranza esquina con Ing. José Cárdenas Valdés, Colonia República, C.P. 25280 Saltillo, Coahuila, Mexico
| | - Diana Luque-Contreras
- Facultad de Ciencias Químicas, Universidad Autónoma de Coahuila, Boulevard Venustiano Carranza esquina con Ing. José Cárdenas Valdés, Colonia República, C.P. 25280 Saltillo, Coahuila, Mexico
| | - Miguel Chin-Chan
- Facultad de Ciencias Químico-Biológicas, Universidad Autónoma de Campeche, Av. Universidad s/n, Col. Buenavista, C.P. 24039 Campeche, Campeche, Mexico
| |
Collapse
|
6
|
Cobos-Puc LE, Sánchez-López A, Centurión D. Pharmacological analysis of the cardiac sympatho-inhibitory actions of moxonidine and agmatine in pithed spontaneously hypertensive rats. Eur J Pharmacol 2016; 791:25-36. [DOI: 10.1016/j.ejphar.2016.08.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 08/03/2016] [Accepted: 08/22/2016] [Indexed: 02/02/2023]
|
7
|
α2A-adrenoceptors, but not nitric oxide, mediate the peripheral cardiac sympatho-inhibition of moxonidine. Eur J Pharmacol 2016; 782:35-43. [DOI: 10.1016/j.ejphar.2016.04.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 04/18/2016] [Accepted: 04/20/2016] [Indexed: 11/30/2022]
|
8
|
Pinacho-García M, Marichal-Cancino BA, Villalón CM. Further evidence for the role of histamine H3, but not H1, H2 or H4, receptors in immepip-induced inhibition of the rat cardioaccelerator sympathetic outflow. Eur J Pharmacol 2016; 773:85-92. [PMID: 26826593 DOI: 10.1016/j.ejphar.2016.01.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 12/03/2015] [Accepted: 01/26/2016] [Indexed: 11/25/2022]
Abstract
Since histamine H3 and H4 receptors are coupled to heterotrimeric Gi/o proteins, a signal transduction pathway associated with inhibition of neurotransmitter release, the present study has investigated the inhibition of the rat cardioaccelerator sympathetic outflow induced by the H3/H4 receptor agonist immepip by using antagonists for histamine H1 (ketotifen), H2 (ranitidine), H3 (thioperamide) and H4 (JNJ7777120) receptors. For this purpose, 102 male Wistar rats were pithed, artificially ventilated and prepared for either preganglionic spinal (C7-T1) stimulation of the cardioaccelerator sympathetic outflow (n=90) or i.v. bolus injections of noradrenaline (n=12). This approach resulted in frequency-dependent and dose-dependent tachycardic responses, respectively. I.v. continuous infusions of immepip (3 and 10 μg/kg min), but not of saline (0.02 ml/min), dose-dependently inhibited the sympathetically-induced tachycardic responses. Moreover, the cardiac sympatho-inhibition induced by 10 μg/kg min immepip (which failed to affect the tachycardic responses to i.v. noradrenaline) was: (i) unaltered after i.v. treatment with 1 ml/kg vehicle, 100 μg/kg ketotifen, 3000 μg/kg ranitidine, 30 μg/kg thioperamide or 300 μg/kg JNJ7777120; and (ii) abolished after 100 μg/kg thioperamide (i.v.). These doses of antagonists, which did not affect per se the sympathetically-induced tachycardic responses, were high enough to block their respective receptors. In conclusion, the cardiac sympatho-inhibition induced by 10 μg/kg.min immepip involves histamine H3 receptors, with further pharmacological evidence excluding the involvement of H1, H2 and H4 receptors.
Collapse
Affiliation(s)
- Manuel Pinacho-García
- Departamento de Farmacobiología, Cinvestav-Coapa, Czda. de los Tenorios No. 235, Col. Granjas-Coapa, Deleg. Tlalpan, 14330 México D.F., México.
| | - Bruno A Marichal-Cancino
- Departamento de Farmacobiología, Cinvestav-Coapa, Czda. de los Tenorios No. 235, Col. Granjas-Coapa, Deleg. Tlalpan, 14330 México D.F., México.
| | - Carlos M Villalón
- Departamento de Farmacobiología, Cinvestav-Coapa, Czda. de los Tenorios No. 235, Col. Granjas-Coapa, Deleg. Tlalpan, 14330 México D.F., México.
| |
Collapse
|
9
|
Altamirano-Espinoza AH, Manrique-Maldonado G, Marichal-Cancino BA, Villalón CM. Specific role of α2A - and α2B -, but not α2C -, adrenoceptor subtypes in the inhibition of the vasopressor sympathetic out-flow in diabetic pithed rats. Basic Clin Pharmacol Toxicol 2014; 117:31-8. [PMID: 25407049 DOI: 10.1111/bcpt.12354] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 11/11/2014] [Indexed: 11/30/2022]
Abstract
Several lines of evidence have shown an association of diabetes with a catecholamines' aberrant homeostasis involving a drastic change in the expression of adrenoceptors. This homeostatic alteration includes, among other things, atypical actions of α2 -adrenoceptor agonists within central and peripheral α2 -adrenoceptors (e.g. profound antinociceptive effects in diabetic subjects). Hence, this study investigated the pharmacological profile of the α2 -adrenoceptor subtypes that inhibit the vasopressor sympathetic out-flow in streptozotocin-pre-treated (diabetic) pithed rats. For this purpose, B-HT 933 (up to 30 μg/kg min) was used as a selective α2 -adrenoceptor agonist and rauwolscine as a non-selective α2A/2B/2C -adrenoceptor antagonist; in addition, BRL 44408, imiloxan and JP-1302 were used as subtype-selective α2A -, α2B - and α2C -adrenoceptor antagonists, respectively (all given i.v.). I.v. continuous infusions of B-HT 933 inhibited the vasopressor responses induced by electrical sympathetic stimulation without affecting those by i.v. bolus injections of noradrenaline in both normoglycaemic and diabetic rats. Interestingly, the ED50 for B-HT 933 in diabetic rats (25 μg/kg min) was almost 1-log unit greater than that in normoglycaemic rats (3 μg/kg.min). Moreover, the sympatho-inhibition induced by 10 μg/kg min B-HT 933 in diabetic rats was (i) abolished by 300 μg/kg rauwolscine or 100 and 300 μg/kg BRL 44408; (ii) partially blocked by 1000 μg/kg imiloxan; and (iii) unchanged by 1000 μg/kg JP-1302. Our findings, taken together, suggest that B-HT 933 has a less potent inhibitory effect on the sympathetic vasopressor responses in diabetic (compared to normoglycaemic) rats and that can probably be ascribed to a down-regulation of α2C -adrenoceptors.
Collapse
Affiliation(s)
| | | | | | - Carlos M Villalón
- Deparment of pharmaco-biology, Cinvestav-Coapa, Tlalpan, Mexico D.F., Mexico
| |
Collapse
|
10
|
Alcántara-Vázquez O, Villamil-Hernández MT, Sánchez-López A, Centurión D. Pharmacological evidence that dopamine inhibits the cardioaccelerator sympathetic outflow via D2-like receptors in pithed rats. J Pharmacol Sci 2013; 123:380-91. [PMID: 24225403 DOI: 10.1254/jphs.13104fp] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
It has been suggested that N,N-di-n-propyl-dopamine (dopamine analogue) decreased heart rate in rats through stimulation of dopamine receptors. Nevertheless, the role of prejunctional dopamine D1/2-like receptors or even α2-adrenoceptors to mediate cardiac sympatho-inhibition induced by dopamine remains unclear. Hence, this study identified the pharmacological profile of the cardiac sympatho-inhibition to dopamine in pithed rats. Male Wistar rats were pithed and prepared to stimulate the cardiac sympathetic outflow or to receive i.v. bolus of exogenous noradrenaline. I.v. continuous infusions of dopamine (endogenous ligand) or quinpirole (D2-like agonist) dose-dependently inhibited the tachycardic responses to sympathetic stimulation, but not those to exogenous noradrenaline. In contrast, SKF-38393 (100 μg/kg∙min, D1-like agonist) failed to modify both of these responses. The sympatho-inhibition to dopamine (1.8 μg/kg∙min) or quinpirole (100 μg/kg∙min): i) remained unaltered after saline or the antagonists SCH-23390 (D1-like, 300 μg/kg) and rauwolscine (α2-adrenoceptors, 300 μg/kg); and ii) was significantly antagonized by raclopride (D2-like, 300 μg/kg). These antagonists, at the above doses, failed to modify the sympathetically-induced tachycardic responses. The above results suggest that the inhibition of the cardiac sympathetic outflow to dopamine and quinpirole is primarily mediated by prejunctional D2-like receptors but not D1-like receptors or α2-adrenoceptors.
Collapse
|
11
|
The α2-adrenoceptors mediating inhibition of the vasopressor sympathetic outflow in pithed rats: Pharmacological correlation with α2A, α2B and α2C subtypes. Eur J Pharmacol 2013; 718:245-52. [DOI: 10.1016/j.ejphar.2013.08.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/04/2013] [Accepted: 08/05/2013] [Indexed: 11/21/2022]
|
12
|
Bhalla S, Ali I, Andurkar SV, Gulati A. Centhaquin antinociception in mice is mediated by α2A- and α2B- but not α2C-adrenoceptors. Eur J Pharmacol 2013; 715:328-36. [DOI: 10.1016/j.ejphar.2013.05.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 04/25/2013] [Accepted: 05/05/2013] [Indexed: 10/26/2022]
|
13
|
Pharmacological identification of the α2-adrenoceptor subtypes mediating the vasopressor responses to B-HT 933 in pithed rats. Eur J Pharmacol 2012; 691:118-24. [DOI: 10.1016/j.ejphar.2012.06.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 06/04/2012] [Accepted: 06/09/2012] [Indexed: 11/21/2022]
|
14
|
Cobos-Puc LE, Villalón CM, Ramírez-Rosas MB, Sánchez-López A, Lozano-Cuenca J, Gómez-Díaz B, MaassenVanDenBrink A, Centurión D. Pharmacological characterization of the inhibition by moxonidine and agmatine on the cardioaccelerator sympathetic outflow in pithed rats. Eur J Pharmacol 2009; 616:175-82. [DOI: 10.1016/j.ejphar.2009.06.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Revised: 05/19/2009] [Accepted: 06/03/2009] [Indexed: 11/30/2022]
|
15
|
Pharmacological profile of the inhibition by dihydroergotamine and methysergide on the cardioaccelerator sympathetic outflow in pithed rats. Eur J Pharmacol 2009; 612:80-6. [DOI: 10.1016/j.ejphar.2009.03.072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Revised: 02/20/2009] [Accepted: 03/31/2009] [Indexed: 11/23/2022]
|
16
|
Pharmacological characterization of ergotamine-induced inhibition of the cardioaccelerator sympathetic outflow in pithed rats. Naunyn Schmiedebergs Arch Pharmacol 2008; 379:137-48. [DOI: 10.1007/s00210-008-0339-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Accepted: 07/09/2008] [Indexed: 11/26/2022]
|
17
|
Villalón CM, Albarrán-Juárez JA, Lozano-Cuenca J, Pertz HH, Görnemann T, Centurión D. Pharmacological profile of the clonidine-induced inhibition of vasodepressor sensory outflow in pithed rats: correlation with alpha(2A/2C)-adrenoceptors. Br J Pharmacol 2008; 154:51-9. [PMID: 18297098 DOI: 10.1038/bjp.2008.49] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Resistance blood vessels are innervated by sympathetic and primary sensory nerves, which modulate vascular tone through the release of noradrenaline and calcitonin gene-related peptide (CGRP), respectively. Moreover, electrical stimulation of the perivascular sensory outflow in pithed rats results in vasodepressor responses which are mainly mediated by CGRP release. The present study has investigated the role of alpha(2)-adrenoceptors in the inhibition of these vasodepressor responses. EXPERIMENTAL APPROACH 144 pithed male Wistar rats were pretreated with hexamethonium (2 mg kg(-1) min(-1)) followed by i.v. continuous infusions of either methoxamine (15 and 30 microg kg(-1) min(-1)) or clonidine (3, 10 and 30 microg kg(-1) min(-1)). Under these conditions, electrical stimulation (0.56-5.6 Hz; 50 V and 2 ms) of the spinal cord (T(9)-T(12)) resulted in frequency-dependent decreases in diastolic blood pressure. KEY RESULTS The infusion of clonidine (10 microg kg(-1) min(-1)), as compared to those of methoxamine (15 or 30 microg kg(-1) min(-1)), inhibited the vasodepressor responses to electrical stimulation without affecting those to i.v. bolus injections of alpha-CGRP (0.1-1 microg kg(-1)). This inhibition by clonidine was: (i) antagonized by 300 microg kg(-1) rauwolscine (alpha(2A/2B/2C)), 300 and 1000 microg kg(-1) BRL44408 (alpha(2A)), or 10 and 30 microg kg(-1) MK912 (alpha(2C)); and (ii) unaffected by 1 ml kg(-1) saline, 100 microg kg(-1) BRL44408, 3000 and 10,000 microg kg(-1) imiloxan (alpha(2B)) or 3 microg kg(-1) MK912. CONCLUSIONS AND IMPLICATIONS The inhibition produced by 10 microg kg(-1) min(-1) clonidine on the vasodepressor (perivascular) sensory outflow in rats may be mainly mediated by prejunctional alpha(2A)/alpha(2C)-adrenoceptors.
Collapse
Affiliation(s)
- C M Villalón
- Departamento de Farmacobiología, Cinvestav-Coapa, Tlalpan, México DF, Mexico.
| | | | | | | | | | | |
Collapse
|
18
|
Kató E, Lipták L, Shujaa N, Mátyus P, Gyires K, Rónai AZ. α2B-adrenoceptor agonist ST-91 antagonizes β2-adrenoceptor-mediated relaxation in rat mesenteric artery rings. Eur J Pharmacol 2008; 580:361-5. [DOI: 10.1016/j.ejphar.2007.09.046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 08/17/2007] [Accepted: 09/07/2007] [Indexed: 11/28/2022]
|