Regional blood flow in conscious rats after head-down suspension

Somody, Laurence; S, Fagette; Blanc, Stéphane; Frutoso, J.; Gharib, Claude; Gauquelin‐Koch, Guillemette

doi:10.1007/s004210050423

Cited by 12 publications

(18 citation statements)

References 25 publications

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“…The well-maintained innervation density we found after long-term head-down tilting might correlate with an increased muscle blood flow, observed by Somody et al [27] in head-down suspended rats. In their model, the animals were tail-suspended with a head-down angle position of 30-35° and were able to move about the cage with their forelimbs in a 360° arch.…”

Section: Discussionsupporting

confidence: 81%

“…Hind-limb and forelimb muscle blood flows were elevated by more than 80 and 215%, respectively, following the 2-week suspension period. Increased muscle activity (and an increased load) might explain the higher blood flows [27]. It is worth mentioning that α-adrenergic vascular responsiveness to calf sympathetic nerve activity was found intact after 2 weeks of head-down bed rest in humans [28].…”

Section: Discussionmentioning

confidence: 95%

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Does Chronic Experimental Head-Down Tilt Alter Intramural Innervation Density of Limb Blood Vessels?

Lorant¹,

Raffai²,

Nádasy³

et al. 2005

JJP

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Earlier, substantial increases in the intramural sympathetic innervation density of rat hind-limb blood vessels were found after 2 weeks of experimental orthostasis with tubular 45° headup tilt cages. In the present study, we presumed that chronic head-down tilting induces opposite changes in the innervation density. Tilted rats were kept 45° head-down in long tubular cages for either 2 or 4 weeks (HDT2, HDT4), and the control animals were maintained in horizontal tilt cages for the same period (HOR2, HOR4). Segments of the saphenous and brachial veins and arteries were used for quantitative electron microscopic examinations. Intramural innervation density was defined by nerve terminal density (NTD) and synaptic microvesicle count (SVC) within the vascular Our previous work, applying a novel chronic 45°head-up tilt model of orthostasis [1,2], revealed several long-term vascular mechanisms supporting orthostatic tolerance in the hind limbs [3]. These mechanisms include an enhancement of the acute-pressure-induced myogenic response of saphenous vein with increases in smooth muscle cell count and in passive vessel diameter without much change in the wall thickness [1,[4][5][6]. Chronic head-up tilt also influences the microcirculatory network properties. A significant rarefaction of microvessels was found in the hind-limb oxidative skeletal muscles of rat after two weeks of orthostasis [7]. Branching angles decreased, and vessel diameters increased in the superficial venous system of the saphenous region of rats in response to long-term orthostasis [8]. The amount of electron-dense vesicles of ap- adventitia. Neither HDT2 nor HDT4 resulted in a decrease of NTD or SVC of the saphenous and brachial veins or arteries; instead, a tendency to increase was observed in some cases. Thus, in contrast to the large increases we found earlier in hind-limb vascular innervation density after 2 weeks of head-up tilting, head-down tilting of the same duration-or even twice as long-did not decrease the adventitial innervation density in our model. We assume that the quasi-free locomotor exercise the tilted animals in the long tubular cages were allowed may counteract a possible suppressive effect of chronic head-down tilt on hind-limb vascular innervation density. [The Japanese Journal of Physiology 55: [127][128][129][130][131][132][133][134] 2005] Key words: brachial vein, head-down tilt, saphenous artery, saphenous vein, vascular innervation.proximately 0.1-0.2 µm diameter (which we identified in the endothelium cells of rat saphenous vein) greatly decreased during two weeks of orthostatic body position [9,10].After 2 weeks of 45° head-tilting, among the most interesting observations we made in this model of orthostasis was a surprisingly large increase (nearly double) in the adventitial (intramural) sympathetic innervation density of hind-limb blood vessels, especially the veins [2]. This increase included both the density of nerve terminals (NTD) and the number of synaptic microvesicles in the terminals (SVC). The...

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 95%

Does Chronic Experimental Head-Down Tilt Alter Intramural Innervation Density of Limb Blood Vessels?

Lorant¹,

Raffai²,

Nádasy³

et al. 2005

JJP

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“…Moreover, after release from 2 weeks of suspension only a transient hypotension has been observed (Somody et al 1998), but if blood pressure is recorded for an hour or more after release from suspension it does not dier from the control values (Fagette et al 1995a;Somody et al 1998;Kharchenko et al 1999). Tachycardia is also transient, lasting not longer than an hour (Fagette et al 1995a;Somody et al 1998). Thus, our data showing an absence of noticeable changes in cardiovascular variables in the rats with an intact sympathetic system during suspension and after resuming the normal body position are in good agreement with the literature.…”

Section: Discussionmentioning

confidence: 93%

“…The MAP and heart rate are somewhat elevated during the ®rst days of suspension (Stump et al 1990), but do not dier from these indices in control rats if the duration of suspension is 1 week or longer (McDonald et al 1992;Fagette et al 1995a;Somody et al 1998;Kharchenko et al1999). Moreover, after release from 2 weeks of suspension only a transient hypotension has been observed (Somody et al 1998), but if blood pressure is recorded for an hour or more after release from suspension it does not dier from the control values (Fagette et al 1995a;Somody et al 1998;Kharchenko et al 1999). Tachycardia is also transient, lasting not longer than an hour (Fagette et al 1995a;Somody et al 1998).…”

Section: Discussionmentioning

confidence: 96%

Effect of tail suspension on haemodynamics in intact and sympathectomized rats

Tarasova

Figourina²,

Зотов

et al. 2001

European Journal of Applied Physiology

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The effect of a 2-week tail suspension on mean arterial pressure (MAP) and pulse interval (PI) was studied in conscious chronically instrumented intact and sympathectomized rats. Sympathectomy was induced by 6-hydroxydopamine (100 mg x kg(-1), i.v.), injected 1 day before, and on days 5 and 10 of suspension. During suspension the intact rats had the same levels of MAP and PI as the intact controls. After release from suspension their MAP did not change: PI decreased (by 9%), but only for 1 h. Sympathectomy augmented the haemodynamic changes after release from suspension: tachycardia (10%) and hypotension (19%) were observed during the entire recording period (2 h). Therefore, in rats, post-suspension hypotension becomes apparent only after elimination of sympathetic influences. In spite of unaltered systemic parameters, intact post-suspension rats showed diminished responses to intravenous administration of tyramine (100 microg x kg(-1)) and phenylephrine (1-2 microg x kg(-1)). In addition, they showed augmented haemodynamic changes associated with natural behaviour. The increase of MAP and the decrease of PI on transition from rest to movement were more pronounced in the intact post-suspension rats than in the control rats (MAP 8.3% vs 4.5%, PI 15% vs 9%). In control rats the spectrum power density of low-frequency (0.0195-0.25 Hz) MAP fluctuations depended only weakly on behavioural activity, whereas in post-suspension intact rats it was profoundly augmented during movements (by 170%). Since the rapid adjustment of haemodynamics to behavioural activity is controlled by the sympathetic nervous system, the unbalanced condition of the cardiovascular system after suspension may reflect an altered sympathetic nerve control of the circulation.

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“…acetaminophen is totally (F ¼ 80-90%) [70,71] and rapidly absorbed (t max ¼ 12-19 min) [33,72] through the intestinal wall by passive diffusion [73], and so consequently its absorption profile depends directly on the rate of gastric emptying. Somody et al [75] studied the regional blood flow in conscious rats after horizontal tail-attachment (all four paws on the floor) and tail-suspension (Morey-Holton model). An oral dose of acetaminophen (100 mg/kg) was administered and blood samples were collected before and at regular intervals up to 12 h after administration.…”

Section: Animal Modelsmentioning

confidence: 99%

The influence of weightlessness on pharmacokinetics

Gandia

Saivin

Houin

2005

Fundamemntal Clinical Pharma

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The primary hostile factor during a spaceflight is the lack of gravity, which can induce space motion sickness and act on bones, muscles and the cardiovascular system. These physiological effects may modify the pharmacokinetics of the drugs administered during the flight producing reduced pharmacological activity or appearance of adverse effects. Given the small number of spaceflights and the difficulties of conducting experiments during missions, pharmacokinetic data obtained in flight are insufficient to determine if drug monitoring is necessary for the drugs present in the onboard medical kit. Therefore, validated earthbound models like tail-suspension performed with animals and long-term bedrest performed with human volunteers are used to simulate weightlessness and to study the pharmacokinetic variations of either absorption, distribution, or elimination of drugs. As a result of these studies, it is possible to make some dosing recommendations but more information is necessary to predict with precision all of the pharmacokinetic variations occurring in spaceflight. To collect more pharmacokinetic information, head-down bedrest studies are still the best solution and as saliva is an appropriate substitution for plasma for some drugs, salivary sampling can be planned during flights.

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Regional blood flow in conscious rats after head-down suspension

Cited by 12 publications

References 25 publications

Does Chronic Experimental Head-Down Tilt Alter Intramural Innervation Density of Limb Blood Vessels?

Does Chronic Experimental Head-Down Tilt Alter Intramural Innervation Density of Limb Blood Vessels?

Effect of tail suspension on haemodynamics in intact and sympathectomized rats

The influence of weightlessness on pharmacokinetics

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