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Biomedical subjects

H H Lu

Publications and source records attributed to H H Lu.

At least 55 records · Page 3Linked to original sources
PubMed1982

Adrenergic receptors and increased reactivity of aortic smooth muscle in renal hypertensive rats.

The contractile responses of aortic smooth muscle and the dissociation constant (Ka) of the norepinephrine (NE) acting on alpha-adrenergic receptors in isolated thoracic aorta from normotensive and renal hypertensive rats were studied. Male Wistar rats were made hypertensive by uninephrectomy with figure-of-eight ligatures around the contralateral kidney. Two to three weeks after operation, the arterial systolic pressure for sham-operated rats was 123 +/- 2, and that for hypertensive rats was 164 +/- 4 mm Hg. Spontaneous rhythmic contractions of aortic rings, which were potentiated by low [Na]o and abolished by nifedipine (10(-6) - 10(-5) M), were observed in 4 out of 18 hypertensive rats. Aortic rings from normotensive rats showed no spontaneous rhythmicity. Although rhythmic phasic contractions could be induced in normotensive tissues by NE or caffeine in the presence of NE, tissues of hypertensive rats responded more readily. Furthermore, the threshold and the ED50 for tonic contractile response to NE was lower in hypertensive aortic rings than in the rings obtained from normotensive aortas. The Ka of NE acting on alpha-adrenergic receptors was derived from concentration-response data for NE before and after irreversible blockade of a fraction of the receptors with dibenamine (1-2 X 10(-7) M) in the presence of cocaine and propranolol. Mean Kas obtained were 5.58 +/- 0.42 X 10(-7) and 2.12 +/- 0.28 X 10(-7) M for normotensive and hypertensive rats, respectively. The increased contractile responses of the hypertensive aorta may be explained, at least partially, by a higher resting [Ca]i and a greater affinity of NE acting on the alpha-adrenergic receptors.

Acetylcholine↗
PubMed1978

Vascular reactivity of isolated perfused kidneys from normotensive, renal hypertensive and spontaneously hypertensive rats.

By means of an isolated kidney perfusion technique, reactivities of renal body vessels to electrical stimulation of renal plexus and intravascular administrations of low dosed norepinephrine and epinephrine were determined in the spontaneously hypertensive rats of Wistar strain, normotensive Sprague-Dawley rats and Sprague-dawley rats with renal hypertension of the same sex and as equal as possible with respect to age and body weight. The basal vascular resistance as indicated by the perfusion pressure caused by the same rat of perfusion was significantly higher in the renal hypertensive group. Both electrical stimulation of the renal plexus and intravascular administrations of catecholamines caused a rise of perfusion pressure. Analysis of the dose-response relationship reveals that in the dose range used, the sensitivities to electrical stimulation and to norepinephrine are significantly higher in the normotensive than the hypertensive groups. The results indicate that structural change in the blood vessels is more important than the adrenergic actions of low intensity in the cause of high resistance of blood flow in hypertensive subjects at least in the kidney.

Animals↗
PubMed1966

Activity of neurones in the paraventricular nucleus of the hypothalamus and its control.

1. Activity of the paraventricular nucleus neurones was recorded by micro-electrodes during resting conditions and while various osmotic, chemical, direct and indirect neural stimuli were applied. This activity was correlated with evidence of oxytocin release by recording milk ejection responses.2. Seventy-four per cent of all paraventricular nucleus neurones were osmosensitive in that firing was augmented following close arterial injection of hypertonic solutions (1 ml. 1 M-NaCl in 10-15 sec). A very few neurones showed decreased activity and in twenty-two per cent no change at all occurred following injection. Evidence indicated that the observed depressions of cellular firing rate were due to other than osmotic stimulation.3. In post-partum cats an osmotically-induced neurone discharge increase was accompanied by a milk ejection response equivalent to that produced by 2-3 m-u. of oxytocin.4. Paraventricular neurones were also sensitive to acetylcholine. Intracarotid injections of 40-80 mug of acetylcholine greatly increased discharge rates and caused a very definite milk ejection response.5. Stimulation of the nipples by gentle suction, but not by electrical shock, and distension of the uterus in post-partum cats increased unit discharge in the paraventricular nucleus and evoked a milk ejection response.6. Neurones of the paraventricular nucleus, unlike those of the supraoptic nucleus, did not appear to be specifically responsive to electrical stimulation of skin and muscle afferent or of central nervous structures. Such stimuli did cause slight augmentations or depressions in firing rates of cells within and adjacent to the paraventricular nuclei, but many neurones were unaffected. Stimuli such as those applied appeared to have a general central effect involving paraventricular as well as many other neurones.7. Direct electrical excitation of the pituitary stalk produced a milk ejection response in post-partum cats. Electrical pulses applied to the paraventricular nuclei were less effective for reasons discussed.

Acetylcholine↗