Revista argentina de cardiología
versión On-line ISSN 1850-3748
MAYER, Marcos A. et al. Role of the Hypothalamus in Blood Pressure Regulation in a Model of Hypertension and Insulin Resistance. Rev. argent. cardiol. [online]. 2007, vol.75, n.2, pp. 117-123. ISSN 1850-3748.
Objective To assess the role of the anterior hypothalamic area in blood pressure regulation in a rat model of hypertension (HTN) and insulin resistance. Material and Methods Seventy-two Sprague-Dawley male rats were divided in two groups, F: fructose group (10% p/v for 6 weeks) and C: control group. The left carotid artery was cannulated to measure mean blood pressure (MBP) and heart rate (HR). A microdialysis probe was placed in the anterior hypothalamic area (AHA) to perfuse yohimbine (10 and 100 µg/ml) or clonidine (100 and 300 µg/ml), an α2-adrenergic antagonist and agonist, respectively; subsequently, hemodynamic changes were assessed. Results Animals in group F had higher systolic blood pressures than animals in group C (F: 131 ± 3 mm Hg versus C: 112 ± 4 mm Hg; p < 0.05). Intrahypothalamic perfusion of yohimbine induced an increase in MBP in group C, whereas values were unchanged in group F. No changes in HR were noted in any of the two groups. Clonidine at a dose of 100 µg/ml induced a decrease in MBP only in group F, whereas the dose of 300 µg/ml induced a decrease in both groups and was greater in F than in C. Only clonidine at a dose of 300 µg/ml decreased HR in group F, while values in group C were unchanged. Conclusions The á2-adrenergic tone would be lower in the AHA of rats in group F, which might be related to the increase in blood pressure seen in that group. Also, the excessive response to clonidine in group F would support the presence of supersensitivity in hypothalamic adrenergic receptors, possibly as a consequence of reduced extracellular levels of noradrenaline in the AHA in this model of HTN and insulin resistance.
Palabras llave : Hypertension; Hypothalamus; Fructose; Receptors; Adrenergic; Microdialysis.