Chronic activation of central α2-adrenoceptors prevents hypertension in DOCA-salt rats
| Autor: | Catia Rocha Gardioli, Antonio M. Cabral, Ilce Ferreira da Silva, Rubia Grecco Menegaz |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Male
Xylazine medicine.medical_specialty Mean arterial pressure Hypertension Renal Sympathetic Nervous System Diuresis Blood Pressure Kidney Nephrectomy Natriuresis Cellular and Molecular Neuroscience Heart Rate Receptors Adrenergic alpha-2 Internal medicine medicine Animals Kidney surgery Rats Wistar Desoxycorticosterone Adrenergic alpha-Antagonists Injections Intraventricular Endocrine and Autonomic Systems business.industry Yohimbine Sodium Dietary Rats Blood pressure Endocrinology Renal physiology Neurology (clinical) business Adrenergic alpha-Agonists medicine.drug |
| Zdroj: | Autonomic Neuroscience. 82:146-153 |
| ISSN: | 1566-0702 |
| DOI: | 10.1016/s0165-1838(00)00093-x |
| Popis: | The effects of chronic intracerebroventricular (i.c.v.) injections of the alpha2-adrenoceptor agonist, xylazine, on blood pressure were examined in DOCA-salt rats. Acute studies also examined the renal sympathetic nerve activity (RSNA) and renal excretory responses produced by i.c.v. xylazine in rats with established DOCA-salt hypertension. Rats implanted with a chronic i.c.v. cannula for drug injection were used. In chronic studies, four groups were investigated: control rats treated with s.c. soybean oil and i.c.v. saline; DOCA-salt rats (s.c. deoxycorticosterone acetate) receiving i.c.v. saline, xylazine or the alpha2-adrenoceptor antagonist, yohimbine. During vehicle or DOCA-salt treatment, xylazine (0.2 ng/microg) or yohimbine (10O microg/kg) was injected i.c.v. daily (three times). In DOCA-salt rats receiving i.c.v. saline, resting mean arterial pressure (MAP) was elevated on days 15 and 30 (135 +/- 5 and 160 +/- 6 mmHg, respectively). Chronic i.c.v. xylazine significantly attenuated the rise in MAP produced by DOCA-salt (day 15, 118 +/- 5 mmHg; day 30, 121 +/- 4 mmHg). Alternatively, chronic i.c.v. yohimbine shortened the onset (day 15, 152 +/- 7 mmHg) and augmented the hypertension in DOCA-salt rats (0 survival by day 30). In acute studies, i.c.v. xylazine elicited a profound natriuresis and diuresis as well as a reduction in RSNA without altering MAP. This study demonstrates that the ongoing (tonic) activity of central alpha2-adrenoceptor mechanisms are critically involved in regulating blood pressure in the DOCA-salt treated rat. In this manner, an enhanced activity of central alpha2-adrenoceptor systems acts to protect against a rise in blood pressure. In contrast, the attenuation of central alpha2-adrenoceptor stimulation evokes hypertension. The central action of xylazine to prevent hypertension may be associated with the inhibition of sympathetic outflow to the kidneys and evokes an enhanced natriuresis. By inhibiting the avid sodium retention elicited by DOCA-salt treatment, the central activation of alpha2-adrenoceptors delays the onset and the severity of hypertension in this pathological model. |
| Databáze: | OpenAIRE |
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