Neurovascular contact and blood pressure response in young, healthy, normotensive men.

BACKGROUND: Neurovascular contact (NVC) of the left rostral ventrolateral medulla has been implicated in the pathogenesis of "essential" hypertension, and recent studies suggest that this anomaly may be genetically determined. We therefore assessed the prevalence of this vascular anomaly in young normotensive volunteers. We also studied blood pressure, heart rate reactivity, and changes in baroreflex sensitivity in response to mental and physical stress in a subset of subjects with positive and negative brainstem findings. METHODS: Magnetic resonance imaging of the brainstem was performed in 113 young (aged 25 +/- 8 years), normotensive male volunteers. Baroreflex sensitivity was then assessed in 13 subjects with positive brainstem findings and 20 subjects with negative findings. RESULTS: Left-sided NVC was found in 19 subjects. Blood pressure levels, heart rate, and baroreflex sensitivity were similar in all groups. However, modulation of baroreflex sensitivity was reduced under mental and physical stress in subjects with a positive finding for NVC. Subjects with a positive finding also had a significantly lower body mass index than those with a negative finding. CONCLUSIONS: Left-sided NVC is present in approximately one-fifth of young normotensive men, and may modulate the baroreceptor reflex under stress in these individuals.

Neurovascular Contact of Cranial Nerve IX and X Root-Entry Zone in Hypertensive Patients.

-Neurovascular contact of the left rostral ventrolateral medulla has been implicated in the pathogenesis of "essential" hypertension, and recent intervention studies suggest that surgical decompression of the ventrolateral medulla lowers blood pressure in these patients. We assessed the prevalence of this vascular anomaly in patients with essential hypertension by using an advanced MRI technique. We performed MRI of the brain stem in 125 hypertensive patients and in 105 age-matched, sex-matched, and body mass index-matched normotensive control subjects. Imaging of the root-entry zone of cranial nerves IX and X was performed by combining a high-resolution 3D constructive interference in steady-state sequence with a flow-sensitive time-of-flight technique, and images were independently assessed by 4 readers using predefined criteria. Left-sided neurovascular contact was found in 23% of the hypertensive patients and in 16% of the normotensive individuals (P:=0.12). Blood pressure level, heart rate, and number of antihypertensive medications in treated hypertensive patients were similar among patients with positive, borderline, and negative brain stem findings. Our findings cast doubt on the importance of left-sided neurovascular contact as a frequent cause of essential hypertension or as a major factor determining the severity of hypertension in patients with this anomaly.

Nitric oxide synthase isoform expression in acute versus chronic anti-Thy 1 nephritis.

BACKGROUND: Two inbred Lewis rat substrains (LEW/Moe, LEW/Maa) were identified responding differently to induction of anti-Thy 1 glomerulonephritis (aThy 1-GN). LEW/Moe rats show an acute mesangioproliferative glomerulonephritis with rapid healing of glomerular lesions within four weeks, while LEW/Maa rats develop severe glomerular injury followed by chronic glomerular sclerosis and persistent albuminuria. We investigated whether the glomerular expression pattern of nitric oxide synthase (NOS) isoforms could explain these substrain-related differences. METHODS: Rats (N = 5 to 7 per group) were investigated in a time course experiment. Severity of aThy 1-GN was determined by albuminuria measurements, glomerular matrix score and microaneurysm formation. Glomerular gene expression of NOS isoforms was determined by semiquantitative RT-PCR. Inducible NOS (iNOS) activity was determined in cultured glomeruli and peritoneal macrophages. Neuronal NOS (nNOS) protein expression was detected by Western blotting and enzyme histochemistry. Plasma renin activity (PRA) was measured by RIA. RESULTS: Induction of iNOS expression and activity was found significantly increased and sustained in LEW/Maa vs. LEW/Moe rats associated with an increased number of infiltrating macrophages and with an increased capacity of iNOS-expression and iNOS-activation by isolated macrophages in LEW/Maa rats. Glomerular nNOS mRNA and nNOS protein expression were constitutively increased in LEW/Maa rats. Renal nNOS localization was restricted to the macula densa region in both substrains and associated with increased PRA in LEW/Maa rats. No difference in glomerular endothelial NOS-mRNA expression between the substrains was observed. CONCLUSIONS: Increased glomerular iNOS and nNOS expression were associated with chronic anti-Thy 1 glomerulonephritis in LEW/Maa rats and may contribute to glomerular damage by separate mechanisms.