Cardiovascular effects of the toxin(s) of the Australian paralysis tick, Ixodes holocyclus, in the rat

Campbell, Fiona and Atwell, Rick and Fenning, Andrew and Hoey, Andrew and Brown, Lindsay (2004) Cardiovascular effects of the toxin(s) of the Australian paralysis tick, Ixodes holocyclus, in the rat. Toxicon, 43 (7). pp. 743-750. ISSN 0041-0101

Abstract

[Abstract]: An extract of toxin(s) from the Australian paralysis tick, Ixodes holocyclus, produced positive inotropic responses in rat left ventricular papillary muscles and positive contractile responses in rat thoracic aortic rings. There was no measurable chronotropic response in rat right atria, but positive inotropic concentrations in papillary muscles produced arrhythmias in right atria. Positive inotropic responses were attenuated by verapamil, but unaffected by metoprolol, cimetidine, pyrilamine, tetrodotoxin and pinacidil. Microelectrode studies on isolated left ventricular papillary muscles demonstrated that the extract prolonged action potential duration at 20, 50 and 90% of repolarisation and delayed ventricular papillary muscle relaxation. Cardiovascular tissues isolated from rats with experimentally induced tick paralysis showed no myocardial damage as identified by histological and ultrastructural examination. The basal rate and force of contraction of isolated cardiac tissues were lower from tick-paralysed than normal rats. Concentration–response curves to dobutamine and calcium chloride were similar between tissues from tick-paralysed and normal rats. Thus, the Australian paralysis tick, I. holocyclus, produces one or more toxins with direct cardiovascular effects which mimic the effects produced by direct blockade of cardiac and vascular Kþ channels.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Author's version not held.
Depositing User: epEditor USQ
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 28 Apr 2010 01:03
Last Modified: 02 Jul 2013 23:49
Uncontrolled Keywords: Australian paralysis tick toxin; cardiovascular responses; Ixodes holocyclus
Fields of Research (FOR2008): 06 Biological Sciences > 0606 Physiology > 060699 Physiology not elsewhere classified
Identification Number or DOI: doi: 10.1016/j.toxicon.2004.02.025
URI: http://eprints.usq.edu.au/id/eprint/7672

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