Microcirculation of the area postrema. Permeability and vascular responses.

Faraci, Frank M.; Choi, James; Baumbach, Gary L.; Mayhan, William G.; Heistad, D D

doi:10.1161/01.res.65.2.417

Cited by 43 publications

(29 citation statements)

References 30 publications

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“…However, we cannot completely rule out the possibility of suppression of brain Ang II activity by enalapril since by long-term administration enaJapril can penetrate the circumventricular organs of the brain such as the area postrema, which has a fenestrated blood-brain barrier. 49 Furthermore, our observations, in which the RSNA range and the range of reflex sympathetic excitation of enalapriltreated SHR did not exceed those of untreated WKY rats and the range of reflex bradycardia was increased by enalapril, may have resulted from the agent's exerting a sympathoinhibitory or a vagomimetic action, or both. 50 ' 51 Therefore, enalapril may exert its effect on baroreceptor reflex sensitivity partially via suppression of brain Ang II activity in addition to blood pressure reduction.…”

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confidence: 59%

Effects of antihypertensive agents on arterial baroreceptor reflexes in conscious rats.

et al. 1992

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The effects of antihypertensive treatment with four currently used agents (trichlormethiazide, atenolol, nicardipine, and enalapril) on the arterial baroreceptor reflex control of renal sympathetic nerve activity and heart rate were investigated in 45 conscious spontaneously hypertensive rats and 37 age-matched Wistar-Kyoto rats. Antihypertensive agents were administered for 2 weeks beginning at 8 weeks of age to treat and prevent the development of hypertension. Blood pressure was reduced to a similar level (-13±3 mm Hg,p<0.05) by each antihypertensive agent Blood pressure, heart rate, and renal sympathetic nerve activity were recorded in the conscious state during phenylephrine and nitroglycerin ramp infusion. The gain in the baroreceptor reflex was determined from the maximum slope of logistic function curves. Untreated spontaneously hypertensive rats exhibited decreased sensitivity of reflex control of renal sympathetic nerve activity and heart rate (-1.78±0.07% of control/mm Hg and -2.16±0.05 beats per minute/mm Hg, respectively) compared with untreated Wistar-Kyoto rats (-3.62±0.18% of control/ mm Hg, p<0.0l, and -3.46±0.11 beats per minute/mm Hg, p<0.05, respectively). The gains in baroreceptor reflex control of renal sympathetic nerve activity and heart rate were greater in trichlormethiazide-(-2.99±0.15%/mm Hg and -3.05±0.13 beats per minute/mm Hg, respectively), atenolol-(-3.22±0.22%/ mm Hg and -3.31 ±0.08 beats per minute/mm Hg, respectively), nicardipine-(-3.48±0.23%/mm Hg and -3.17±0.06 beats per minute/mm Hg, respectively), and enalapril-(-3.11±0.08%/mm Hg and -3-54±0.17 beats per minute/mm Hg, respectively) treated spontaneously hypertensive rats (allp<0.05) than in untreated spontaneously hypertensive rats. The antihypertensive agents affected neither blood pressure nor the baroreceptor reflex function curves in Wistar-Kyoto rats. These results indicate that attenuation of the development of hypertension by the antihypertensive agents is responsible for the restoration of impaired baroreceptor reflex control of renal sympathetic nerve activity and heart rate in conscious early hypertensive spontaneously hypertensive rats, although different antihypertensive mechanisms may mediate the blood pressure reduction. of end-organ damage are the major goals of antihypertensive therapy. Recent advances in clinical pharmacology have provided us with a huge armamentarium of antihypertensive agents. Excessive reduction of blood pressure may decrease the regional organ blood flow, leading to serious complications such as myocardial ischemia, renal dysfunction, cerebral ischemia, and at times even death. Evidence has been provided that an arterial baroreceptor reflex mechanism modifies regional blood flow 1 -2 and that the effectiveness of the baroreceptor reflex mechanism would be very limited if the resetting process was not reversible. 3Restoration of baroreceptor reflex function (i.e., normalization of reflex sensitivity and reversibility of

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confidence: 59%

Effects of antihypertensive agents on arterial baroreceptor reflexes in conscious rats.

et al. 1992

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“…The hypothesis was that, because the blood-brain barrier is absent, circulating humoral stimuli would have pronounced effects on arterioles of the area postrema. 36 To our surprise, intravascular vasopressin did not have selective constrictor effects on arterioles that supply the area postrema. The explanation for these findings became apparent when we observed that the blood-brain barrier, which is absent in capillaries of the area postrema, appears to be present in arterioles to the area postrema.…”

Section: Area Postremamentioning

confidence: 66%

“…The explanation for these findings became apparent when we observed that the blood-brain barrier, which is absent in capillaries of the area postrema, appears to be present in arterioles to the area postrema. 36 Based on these findings, we suggest that, in contrast to the choroid plexus, circulating stimuli such as vasopressin may not have selective effects on blood flow to the area postrema (Figure 2). …”

Section: Area Postremamentioning

confidence: 85%

Regulation of cerebral blood vessels by humoral and endothelium-dependent mechanisms. Update on humoral regulation of vascular tone.

Faraci

Heistad

1991

Hypertension

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C irculating catecholamines and vasoactive peptides play an important role in regulation of the peripheral circulation. These humoral stimuli generally are considered to have little effect on the cerebral circulation. The concept that circulating vasoactive stimuli have minimal effect on cerebral blood flow is based on the observation that cerebral endothelium (the blood-brain barrier) restricts access of many blood-borne substances to cerebral vascular smooth muscle.In this review, we will propose, based on recent findings, revision of the concept that humoral stimuli

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“…The vasculature of the CVOs is apparently different from the typical BBB vasculature of the brains since the CVOs do not express the tight junction proteins [7][8][9][10][11] , and therefore, blood-derived substances are permeable to the vasculature of the CVOs. [12][13][14] Recently, however, we have shown that vascular permeability of low-molecular-mass tracers is lower in the sensory CVOs as compared with that in the secretory CVOs and the kidney, indicating that vascular permeability of the sensory CVOs is largely restricted. 15 In the sensory CVOs, fenestrated vasculature allows parenchyma cells to sense a wide variety of blood-derived substances and convey their information into other brain regions for the control of autonomic and inflammatory reactions and/or behaviours.…”

Section: Introductionmentioning

confidence: 97%

Changes in pericytic expression of NG2 and PDGFRB and vascular permeability in the sensory circumventricular organs of adult mouse by osmotic stimulation

Morita

Hourai

Miyata

2013

Cell Biochemistry & Function

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The blood-brain barrier (BBB) is a barrier that prevents free access of blood-derived substances to the brain through the tight junctions and maintains a specialized brain environment. Circumventricular organs (CVOs) lack the typical BBB. The fenestrated vasculature of the sensory CVOs, including the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO) and area postrema (AP), allows parenchyma cells to sense a variety of blood-derived information, including osmotic ones. In the present study, we utilized immunohistochemistry to examine changes in the expression of NG2 and platelet-derived growth factor receptor beta (PDGFRB) in the OVLT, SFO and AP of adult mice during chronic osmotic stimulation. The expression of NG2 and PDGFRB was remarkably prominent in pericytes, although these angiogenesis-associated proteins are highly expressed at pericytes of developing immature vasculature. The chronic salt loading prominently increased the expression of NG2 in the OVLT and SFO and that of PDGFRB in the OVLT, SFO and AP. The vascular permeability of low-molecular-mass tracer fluorescein isothiocyanate was increased significantly by chronic salt loading in the OVLT and SFO but not AP. In conclusion, the present study demonstrates changes in pericyte expression of NG2 and PDGFRB and vascular permeability in the sensory CVOs by chronic osmotic stimulation, indicating active participation of the vascular system in osmotic homeostasis.

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Microcirculation of the area postrema. Permeability and vascular responses.

Cited by 43 publications

References 30 publications

Effects of antihypertensive agents on arterial baroreceptor reflexes in conscious rats.

Effects of antihypertensive agents on arterial baroreceptor reflexes in conscious rats.

Regulation of cerebral blood vessels by humoral and endothelium-dependent mechanisms. Update on humoral regulation of vascular tone.

Changes in pericytic expression of NG2 and PDGFRB and vascular permeability in the sensory circumventricular organs of adult mouse by osmotic stimulation

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