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The effects of anaesthetics on the reactivity of vascular smooth muscle

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MacPherson, Ross Duncan (1992) The effects of anaesthetics on the reactivity of vascular smooth muscle. PhD thesis, University of Tasmania.

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Abstract

This thesis examines a number of aspects of vascular smooth muscle
physiology and pharmacology. The first set of experiments examines
the mechanisims of the myogenic response in the isolated pressurised
rabbit ear artery preparation, an experimental model developed here in
the University of Tasmania, Department of Physiology.
Rabbit ear artery segments were subjected to pressure changes in the
form of either rapid increases (referred to as jumps) or slow increases
(ramps). The changes in diameter of vessels as they responded to these
pressure alterations were recorded. These same pressure changes were
performed in vessels in four settings: in vessels where the
endothelium had been removed, in vessels constricted with different
vasoconstrictor agents, and at different starting diameters, in vessels
dilated with either acetylcholine or sodium nitroprusside, and in
vessels partly dilated with the calcium channel blocking agent,
nifedipine.
The results demonstrated that the endothelium was not mandatory for
the myogenic response, but that acetylcholine induced endotheliumderived
relaxing factor release could modify the nature of the response,
as could nifedipine. The nature of vasoconstriction, and degree of
constriction of the vessels were not major determinants of
myogenicity.
The effect of the intravenous anaesthetic agent propofol on vascular
smooth muscle was then examined. This relatively recently introduced
drug is known to possess significant hypotensive properties, but the
mechanism of this response is unclear. In a series of experiments using
the rabbit ear artery preparation, it was found that apart from having a
direct vasodilator effect, propofol was a powerful attenuator of
myogenicity - an effect distinct from its smooth muscle relaxant
properties. This may be important in explaining the drugs hypotensive
effect.
Lastly, a series of experiments used the experimental apparatus to
examine the effects of intra-arterial drug administration of both
propofol and thiopentone. Intra-arterial administration of propofol,
from clinical reports does not appear to be associated with serious
hazard, a finding, in part confirmed by studies performed in this series.
However, intra-arterial thiopentone administration was found to
result in an almost complete destruction of the vascular endotheliuman
hitherto unreported event which may well explain the reasons for
the widespread vascular damage and ischaemia associated with
accidental intra-arterial injection.

Item Type: Thesis (PhD)
Keywords: Vascular smooth muscle, Vascular smooth muscle, Anesthetics
Copyright Holders: The Author
Copyright Information:

Copyright 1992 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Includes bibliographical references. Thesis (Ph.D.)--University of Tasmania, 1993

Date Deposited: 19 Dec 2014 02:28
Last Modified: 04 Aug 2017 02:34
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