Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats
Activation of 5-hydroxytryptamine (5-HT) 5-HT1A, 5-HT2C, 5-HT3, and 5-HT7 receptors modulates the excitability of cardiac vagal motoneurones, but the precise role of 5-HT2A/2B receptors in these phenomena is unclear. We report here the effects of intracisternal (ic) administration of selective 5-HT2...
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| Format: | Article |
| Language: | English |
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Associação Brasileira de Divulgação Científica
2011-03-01
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| Series: | Brazilian Journal of Medical and Biological Research |
| Subjects: | |
| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2011000300008 |
| _version_ | 1818611566102183936 |
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| author | H.A. Futuro Neto S.M. Macedo N.F. Silva A.M. Cabral J.G.P. Pires |
| author_facet | H.A. Futuro Neto S.M. Macedo N.F. Silva A.M. Cabral J.G.P. Pires |
| author_sort | H.A. Futuro Neto |
| collection | DOAJ |
| description | Activation of 5-hydroxytryptamine (5-HT) 5-HT1A, 5-HT2C, 5-HT3, and 5-HT7 receptors modulates the excitability of cardiac vagal motoneurones, but the precise role of 5-HT2A/2B receptors in these phenomena is unclear. We report here the effects of intracisternal (ic) administration of selective 5-HT2A/2B antagonists on the vagal bradycardia elicited by activation of the von Bezold-Jarisch reflex with phenylbiguanide. The experiments were performed on urethane-anesthetized male Wistar rats (250-270 g, N = 7-9 per group). The animals were placed in a stereotaxic frame and their atlanto-occipital membrane was exposed to allow ic injections. The rats received atenolol (1 mg/kg, iv) to block the sympathetic component of the reflex bradycardia; 20-min later, the cardiopulmonary reflex was induced with phenylbiguanide (15 µg/kg, iv) injected at 15-min intervals until 3 similar bradycardias were obtained. Ten minutes after the last pre-drug bradycardia, R-96544 (a 5-HT2A antagonist; 0.1 µmol/kg), SB-204741 (a 5-HT2B antagonist; 0.1 µmol/kg) or vehicle was injected ic. The subsequent iv injections of phenylbiguanide were administered 5, 20, 35, and 50 min after the ic injection. The selective 5-HT2A receptor antagonism attenuated the vagal bradycardia and hypotension, with maximal effect at 35 min after the antagonist (pre-drug = -200 ± 11 bpm and -42 ± 3 mmHg; at 35 min = -84 ± 10 bpm and -33 ± 2 mmHg; P < 0.05). Neither the 5-HT2B receptor antagonists nor the vehicle changed the reflex. These data suggest that central 5-HT2A receptors modulate the central pathways of the parasympathetic component of the von Bezold-Jarisch reflex. |
| first_indexed | 2024-12-16T15:32:22Z |
| format | Article |
| id | doaj.art-d62b121476e84a67860d29ff64e8c289 |
| institution | Directory Open Access Journal |
| issn | 0100-879X 1414-431X |
| language | English |
| last_indexed | 2024-12-16T15:32:22Z |
| publishDate | 2011-03-01 |
| publisher | Associação Brasileira de Divulgação Científica |
| record_format | Article |
| series | Brazilian Journal of Medical and Biological Research |
| spelling | doaj.art-d62b121476e84a67860d29ff64e8c2892022-12-21T22:26:18ZengAssociação Brasileira de Divulgação CientíficaBrazilian Journal of Medical and Biological Research0100-879X1414-431X2011-03-01443224228Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized ratsH.A. Futuro NetoS.M. MacedoN.F. SilvaA.M. CabralJ.G.P. PiresActivation of 5-hydroxytryptamine (5-HT) 5-HT1A, 5-HT2C, 5-HT3, and 5-HT7 receptors modulates the excitability of cardiac vagal motoneurones, but the precise role of 5-HT2A/2B receptors in these phenomena is unclear. We report here the effects of intracisternal (ic) administration of selective 5-HT2A/2B antagonists on the vagal bradycardia elicited by activation of the von Bezold-Jarisch reflex with phenylbiguanide. The experiments were performed on urethane-anesthetized male Wistar rats (250-270 g, N = 7-9 per group). The animals were placed in a stereotaxic frame and their atlanto-occipital membrane was exposed to allow ic injections. The rats received atenolol (1 mg/kg, iv) to block the sympathetic component of the reflex bradycardia; 20-min later, the cardiopulmonary reflex was induced with phenylbiguanide (15 µg/kg, iv) injected at 15-min intervals until 3 similar bradycardias were obtained. Ten minutes after the last pre-drug bradycardia, R-96544 (a 5-HT2A antagonist; 0.1 µmol/kg), SB-204741 (a 5-HT2B antagonist; 0.1 µmol/kg) or vehicle was injected ic. The subsequent iv injections of phenylbiguanide were administered 5, 20, 35, and 50 min after the ic injection. The selective 5-HT2A receptor antagonism attenuated the vagal bradycardia and hypotension, with maximal effect at 35 min after the antagonist (pre-drug = -200 ± 11 bpm and -42 ± 3 mmHg; at 35 min = -84 ± 10 bpm and -33 ± 2 mmHg; P < 0.05). Neither the 5-HT2B receptor antagonists nor the vehicle changed the reflex. These data suggest that central 5-HT2A receptors modulate the central pathways of the parasympathetic component of the von Bezold-Jarisch reflex.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X20110003000085-HT2 receptorsR-96544Reflex bradycardiaSB-204741Vagal motoneuronsvon Bezold-Jarisch reflex |
| spellingShingle | H.A. Futuro Neto S.M. Macedo N.F. Silva A.M. Cabral J.G.P. Pires Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats Brazilian Journal of Medical and Biological Research 5-HT2 receptors R-96544 Reflex bradycardia SB-204741 Vagal motoneurons von Bezold-Jarisch reflex |
| title | Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats |
| title_full | Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats |
| title_fullStr | Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats |
| title_full_unstemmed | Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats |
| title_short | Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats |
| title_sort | central 5 ht2a receptors modulate the vagal bradycardia in response to activation of the von bezold jarisch reflex in anesthetized rats |
| topic | 5-HT2 receptors R-96544 Reflex bradycardia SB-204741 Vagal motoneurons von Bezold-Jarisch reflex |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2011000300008 |
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