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Parkin ML, Lim K, Burke SL, et al. Comparison in Conscious Rabbits of the Baroreceptor-Heart Rate Reflex Effects of Chronic Treatment with Rilmenidine, Moxonidine, and Clonidine. Front Physiol. 2016;7:522doi: 10.3389/fphys.2016.00522.
Parkin, M. L., Lim, K., Burke, S. L., & Head, G. A. (2016). Comparison in Conscious Rabbits of the Baroreceptor-Heart Rate Reflex Effects of Chronic Treatment with Rilmenidine, Moxonidine, and Clonidine. Frontiers in physiology, 7522. https://doi.org/10.3389/fphys.2016.00522
Parkin, Monique L, et al. "Comparison in Conscious Rabbits of the Baroreceptor-Heart Rate Reflex Effects of Chronic Treatment with Rilmenidine, Moxonidine, and Clonidine." Frontiers in physiology vol. 7 (2016): 522. doi: https://doi.org/10.3389/fphys.2016.00522
Parkin ML, Lim K, Burke SL, Head GA. Comparison in Conscious Rabbits of the Baroreceptor-Heart Rate Reflex Effects of Chronic Treatment with Rilmenidine, Moxonidine, and Clonidine. Front Physiol. 2016 Nov 15;7:522. doi: 10.3389/fphys.2016.00522. eCollection 2016. PMID: 27895591; PMCID: PMC5108798.
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Front Physiol. 2016 Nov 15;7:522. doi: 10.3389/fphys.2016.00522. eCollection 2016.

Comparison in Conscious Rabbits of the Baroreceptor-Heart Rate Reflex Effects of Chronic Treatment with Rilmenidine, Moxonidine, and Clonidine.

Frontiers in physiology

Monique L Parkin, Kyungjoon Lim, Sandra L Burke, Geoffrey A Head

Affiliations

  1. Neuropharmacology Laboratory, Baker IDI Heart and Diabetes Institute Melbourne, VIC, Australia.

PMID: 27895591 PMCID: PMC5108798 DOI: 10.3389/fphys.2016.00522

Abstract

We investigated the effects of chronic subcutaneous treatment with centrally-acting antihypertensive agents moxonidine, rilmenidine, and clonidine on the baroreflex control of heart rate (HR) in conscious normotensive rabbits over 3 weeks. Infusions of phenylephrine and nitroprusside were performed at week 0 and at weeks 1 and 3 of treatment to determine mean arterial pressure (MAP)-HR baroreflex relationships. A second curve was performed after intravenous methscopolamine to determine the sympathetic baroreflex relationship. The vagal component of the reflex was determined by subtracting the sympathetic curve from the intact curve. Clonidine and moxonidine (both 1 mg/kg/day), and rilmenidine (5 mg/kg/day), reduced MAP by 13 ± 3, 15 ± 2, and 13 ± 2 mmHg, respectively, but had no effect on HR over the 3-week treatment period. Whilst all three antihypertensive agents shifted baroreflex curves to the left, parallel to the degree of hypotension, moxonidine and rilmenidine decreased the vagal contribution to the baroreflex by decreasing the HR range of the reflex but moxonidine also increased sympathetic baroreflex range and sensitivity. By contrast clonidine had little chronic effect on the cardiac baroreflex. The present study shows that second generation agents moxonidine and rilmenidine but not first generation agent clonidine chronically shift the balance of baroreflex control of HR toward greater sympathetic and lesser vagal influences. These changes if translated to hypertensive subjects, may not be particularly helpful in view of the already reduced vagal contribution in hypertension.

Keywords: baroreceptor-heart rate reflex; blood pressure; cardiac sympathetic; cardiac vagus; clonidine; conscious rabbits; moxonidine; rilmenidine

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