Simon J. Potocnik

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The smooth muscle of arterioles responds to an increase in intraluminal pressure with vasoconstriction and with vasodilation when pressure is decreased. Such myogenic vasoconstriction provides a level of basal tone that enables arterioles to appropriately adjust diameter in response to neurohumoral stimuli. Key in this process of mechanotransduction is the(More)
Treatment of nine pregnant Merino ewes (64.0 +/- 0.4 days of gestation) with dexamethasone (D; 0.76 mg/h for 48 h) resulted in significant alterations in fetal fluids compared with eight saline-infused control animals (S; 63.0 +/- 0.9 days). There was a substantial increase in allantoic fluid volume (177 +/- 18 ml, D vs. 31 +/- 6, S) but no change in(More)
1. Ca(2+) entry mechanisms underlying spontaneous arteriolar tone and acute myogenic reactivity remain uncertain. These studies aimed to compare the effects of nifedipine and the putative T-channel blocker, mibefradil, on arteriolar myogenic responsiveness and intracellular Ca(2+) (Ca(2+)(i)). 2. First order cremaster muscle arterioles (1A) were isolated(More)
Arterioles typically exist in a state of partial constriction that is related to the level of intraluminal pressure. This vasomotor response is a function of the vascular smooth muscle and occurs independently of neurohumoral and endothelial input. The physiological relevance of myogenic constriction relates to the setting of peripheral resistance,(More)
OBJECTIVE Given evidence for clustering of signalling molecules and ion channels in cholesterol-rich membrane domains, the involvement of such structures in arteriolar smooth muscle mechanotransduction was examined. METHOD To determine the contribution of smooth muscle cholesterol-rich membrane domains to the myogenic response, isolated arterioles were(More)
1. Acute haemorrhage was simulated in five unanaesthetized rabbits, by inflating a cuff on the inferior vena cava so that cardiac output fell by 8.3% of its resting level per minute. Simulated haemorrhage was performed after sham treatment, after graded doses of intravenous and intracisternal naloxone, and after cardiac nerve blockade with intrapericardial(More)
Five rabbits were allotted to each of six treatments on a matched-individual basis. Treatments were none, sham, total adrenalectomy with adrenocorticoid replacement, intravenous guanethidine (15 mg X kg-1 X day-1), adrenalectomy + guanethidine, and adrenal medullectomy. The conscious rabbits were bled 20 ml/kg over 5 min. Naloxone (6 mg/kg) was injected(More)
Local control of neural blood flow is considered to reside in innervation of epineurial and endoneurial arterioles rather than in intrinsic autoregulatory mechanisms. With the use of an isolated vessel preparation and an in vivo approach, the present studies examined intrinsic vasomotor responsiveness of epineurial arterioles. Segments of epineurial(More)
1. The reproducibility of blood volume measurements, using [51Cr]-labelled red blood cells (RBC) was tested in three lambs, 79-89 days of age, and the accuracy was tested in eight lambs, 83 +/- 0.4 days of age, in which blood volume was measured simultaneously by [51Cr]-RBC and [125I]-gamma globulin plus haematocrit (hct). 2. The blood volumes (mean +/-(More)
We describe the use of a snare to denervate the carotid sinus in conscious rabbits whose other arterial baroreceptors had been denervated 8-14 days previously by surgical operation. Within 2 min of tightening the snare arterial blood pressure had risen from 81 +/- 2 to 119 +/- 5 mmHg, and heart rate had risen from 214 +/- 9 to 280 +/- 9 beats min-1. They(More)