Title |
Central 5-HT2A receptors modulate the vagal bradycardia in response to activation of the von Bezold-Jarisch reflex in anesthetized rats
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Published in |
Brazilian Journal of Medical and Biological Research, February 2011
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DOI | 10.1590/s0100-879x2011007500016 |
Pubmed ID | |
Authors |
H.A. Futuro Neto, S.M. Macedo, N.F. Silva, A.M. Cabral, J.G.P. Pires |
Abstract |
Activation of 5-hydroxytryptamine (5-HT) 5-HT(1A), 5-HT(2C), 5-HT(3), and 5-HT(7) receptors modulates the excitability of cardiac vagal motoneurones, but the precise role of 5-HT(2A/2B) receptors in these phenomena is unclear. We report here the effects of intracisternal (ic) administration of selective 5-HT(2A/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-HT(2A) antagonist; 0.1 µmol/kg), SB-204741 (a 5-HT(2B) 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-HT(2A) 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-HT(2B) receptor antagonists nor the vehicle changed the reflex. These data suggest that central 5-HT(2A) receptors modulate the central pathways of the parasympathetic component of the von Bezold-Jarisch reflex. |
Mendeley readers
Geographical breakdown
Country | Count | As % |
---|---|---|
Unknown | 11 | 100% |
Demographic breakdown
Readers by professional status | Count | As % |
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Researcher | 3 | 27% |
Other | 2 | 18% |
Student > Master | 1 | 9% |
Professor > Associate Professor | 1 | 9% |
Student > Postgraduate | 1 | 9% |
Other | 0 | 0% |
Unknown | 3 | 27% |
Readers by discipline | Count | As % |
---|---|---|
Medicine and Dentistry | 6 | 55% |
Chemistry | 1 | 9% |
Unknown | 4 | 36% |