Overexpression of apelin in the paraventricular nucleus increases blood pressure and sympathetic nerve activity in normotensive rats

The present study was performed to determine whether sympathetic outflow and arterial blood pressure in water-deprived rats are dependent on the ongoing neuronal activity of the hypothalamic paraventricular nucleus (PVN). Renal sympathetic nerve activity (RSNA), mean arterial blood pressure (MAP), and heart rate were recorded in urethane-α-chloralose-anesthetized rats that were deprived of water but not food for 48 h before experiments. Acute inhibition of the PVN by bilateral microinjection of the GABAA agonist muscimol (100 pmol/side) significantly decreased RSNA in water-deprived rats (-26.7 ± 4.7%, n = 7) but was without effect in control rats (1.3 ± 6.3%, n = 7). Similarly, injection of muscimol produced a greater decrease in MAP in water-deprived rats than in control rats (-46 ± 3 vs. -16 ± 3 mmHg, respectively), although baseline MAP was not different between groups (105 ± 4 vs. 107 ± 4 mmHg, respectively). Neither bilateral microinjection of isotonic saline vehicle (100 nl/side) into the PVN nor muscimol (100 pmol/side) outside the PVN altered RSNA or MAP in either group. In addition, ganglionic blockade with hexamethonium (30 mg/kg iv) significantly decreased MAP in both groups; however, the decrease in MAP was significantly greater in water-deprived rats than in control rats (62 ± 2 vs. 48 ± 2 mmHg, respectively). Collectively, these findings suggest that sympathetic outflow contributes more to the maintenance of blood pressure in the water-deprived rat, and this depends, at least partly, on the ongoing activity of PVN neurons.

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Effects of stimulation of the hypothalamic paraventricular nucleus on blood pressure and renal sympathetic nerve activity

Brain Research Bulletin ◽

10.1016/0361-9230(88)90091-3 ◽

1988 ◽

Vol 20 (6) ◽

pp. 779-783 ◽

Cited By ~ 31

Author(s):

H. Kannan ◽

A. Niijima ◽

H. Yamashita

Keyword(s):

Blood Pressure ◽

Paraventricular Nucleus ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Hypothalamic Paraventricular Nucleus ◽

Nerve Activity ◽

Renal Sympathetic Nerve Activity ◽

Renal Sympathetic Nerve ◽

Renal Sympathetic ◽

Stimulation Of

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High-fat feeding alters the cardiovascular role of the hypothalamic paraventricular nucleus

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00558.2009 ◽

2010 ◽

Vol 298 (3) ◽

pp. R799-R807 ◽

Cited By ~ 11

Author(s):

Feng Chen ◽

Joo Lee Cham ◽

Emilio Badoer

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Paraventricular Nucleus ◽

Sympathetic Nerve ◽

High Fat Diet ◽

Sympathetic Nerve Activity ◽

Hypothalamic Paraventricular Nucleus ◽

High Fat ◽

Nerve Activity

Increased sympathetic nerve activity is associated with obesity-related hypertension, but the underlying central neural mechanisms are not clear. We examined the role of the hypothalamic paraventricular nucleus (PVN) in the regulation of sympathetic nerve activity in rats fed a normal chow diet (controls) and rats fed a high-fat diet (36% fat) over 12 wk. The effects on blood pressure, heart rate, and lumbar sympathetic nerve activity (LSNA) induced by microinjection of the GABAA receptor agonist muscimol or the antagonist bicuculline were monitored in anesthetized rats. Body weight of rats fed the high-fat diet was not significantly different from controls, but a significant 80% increase in epididymal fat mass, significantly elevated fasting blood glucose, and significantly impaired glucose tolerance were observed in rats fed the high-fat diet. Resting blood pressure and heart rate were not significantly different between rats fed the high-fat diet and controls. Muscimol microinjected into the PVN elicited a greater reduction of blood pressure and LSNA in rats fed the high-fat diet than controls: −14 ± 6 vs. −7 ± 2 mmHg and −35 ± 6 vs. −10 ± 9% ( P < 0.05). Microinjection of bicuculline into the PVN increased blood pressure and LSNA, but the responses were similar in rats fed the high-fat diet and controls. In conclusion, the role of the paraventricular nucleus in cardiovascular regulation can be altered by a diet high in fat, even when hypertension and obesity are absent.

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