Specific increase of hypothalamic alpha 1-adrenoceptors in spontaneously hypertensive rats: effect of hypotensive drug treatment

Is the spontaneously hypertensive stroke prone rat a pertinent model of sub cortical ischemic stroke? A systematic review

The spontaneously hypertensive stroke prone rat is best known as an inducible model of large artery stroke. Spontaneous strokes and stroke propensity in the spontaneously hypertensive stroke prone rat are less well characterized; however, could be relevant to human lacunar stroke. We systematically reviewed the literature to assess the brain tissue and small vessel pathology underlying the spontaneous strokes of the spontaneously hypertensive stroke prone rat. We searched systematically three online databases from 1970 to May 2010; excluded duplicates, reviews, and articles describing the consequences of induced middle cerebral artery occlusion or noncerebral pathology; and recorded data describing brain region and the vessels examined, number of animals, age, dietary salt intake, vascular and tissue abnormalities. Among 102 relevant studies, animals sacrificed after developing stroke-like symptoms displayed arteriolar wall thickening, subcortical lesions, enlarged perivascular spaces and cortical infarcts and hemorrhages. Histopathology, proteomics and imaging studies suggested that the changes not due simply to hypertension. There may be susceptibility to endothelial permeability increase that precedes arteriolar wall thickening, degeneration and perivascular tissue changes; systemic inflammation may also precede cerebrovascular changes. There were very few data on venules or tissue changes before hypertension. The spontaneously hypertensive stroke prone rat shows similar features to human lacunar stroke and may be a good spontaneous model of this complex human disorder. Further studies should focus on structural changes at early ages and genetics to identify factors that predispose to vascular and brain damage.

Alpha-1-adrenergic receptors in the nucleus tractus solitarii region of rats with experimental and genetic hypertension

The binding of the alpha 1-adrenergic receptors antagonist, 125I-HEAT, to membranes of nucleus tractus solitarii (NTS) regions of the brains of neurogenic hypertensive, spontaneously hypertensive (SH), and deoxycorticosterone (DOCA)/salt hypertensive rats and their respective controls was studied to quantitate the expression of alpha 1-adrenergic receptors. Scatchard analysis of the binding studies revealed a 1.8-fold increase in the Bmax of alpha 1-adrenergic receptors in NTS region membranes of SH rats when compared to their Wistar-Kyoto (WKY) control without significant difference in the Kd for 125I-HEAT. A decrease in the Kd with no difference in Bmax of receptors for 125I-HEAT was observed in the NTS region membranes of neurogenic hypertensive rats when compared with their sham-operated controls. In contrast, comparison of the Bmax and Kd values for 125I-HEAT binding in NTS region membrane of the DOCA/salt hypertensive rats and its sham-operated control showed no significant differences. We suggest that alterations in baroreceptor afferent activity may be related to alterations in central alpha 1-adrenergic receptors binding in SH rats and rats with neurogenic hypertension.

Persistent hypotensive effect of L-dopa given early during development to rats with inherited stress-induced arterial hypertension

A long-lasting decrease of the basal and stress-induced arterial blood pressure was obtained in rats with inherited emotional stress-induced arterial hypertension by means of injections of the dopamine precursor L-DOPA during early development (21-25 days after birth). The restoring effect of L-DOPA was produced through enhancement of synthesis of the brain noradrenaline and, perhaps, adrenaline. The effect was associated with a normalization of the response of the brain adrenergic system to noradrenaline and, presumably, with increase of tyrosine hydroxylase activity in the cortex and hindbrain.

Increased expression of alpha 1-adrenergic receptors in the hypothalamus of spontaneously hypertensive rats

The specificity and molecular weights of alpha 1-adrenergic receptors in various tissues of spontaneously hypertensive (SH) rat were compared with normotensive controls (Wistar-Kyoto; WKY) with the use of [125I]HEAT and [125I]azidoprazosin, specific alpha 1-adrenergic receptor antagonists. Binding of [125I]HEAT to membranes prepared from SH rat brain hypothalamus was significantly higher, due to a 75% increase in the Bmax, than the WKY control. In contrast, the Bmax and Kd of [125I]HEAT binding to brainstem and liver membranes from SH rats were not significantly different from those of WKY controls. Competition-inhibition data suggested similar pharmacological specificity with potencies in the order of prazosin greater than yohimbine greater than propranolol for both WKY and SH rat membranes prepared from liver, hypothalamus, brainstem and neuronal cultures. Photoaffinity labeling of alpha 1-adrenergic receptors from hypothalamus, brainstem and neuronal cultures using [125I]azidoprazosin followed by SDS-PAGE and autoradiography showed the presence of one major band with a molecular weight (MW) of 105,000 Da for both WKY and SH rats. In contrast, labeling of liver alpha 1-adrenergic receptors revealed one major band with a MW of 60,000 Da. Quantitation of the 105,000-Da band from SH rat hypothalamic membranes demonstrated a 52% higher intensity compared with WKY controls. Neuronal cultures prepared from 1-day-old SH rats showed a similarly greater intensity of the 105,000-Da band compared with WKY controls.(ABSTRACT TRUNCATED AT 250 WORDS)