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Canadian Journal of Anesthesia, Vol 42, 944-947, Copyright © 1995 by Canadian Anesthesiologists' Society

ARTICLES

Thiopentone inhibits beta-adrenergic responses in myocardial tissue

TA Thurston and BP Mathew
Department of Anesthesiology, University of Texas Medical Branch at Galveston 77555, USA.

The purpose of this study was to determine the importance of inhibition of beta-adrenergic function in thiopentone-induced myocardial depression. Using an isolated, electrically stimulated rat left atria model, contractile dose-response curves to thiopentone (200 microM, 400 microM, 600 microM, 800 microM) were shifted to the right in preparations treated with 10(-3)M dibutyryl cyclic adenosine monophosphate (cAMP) compared with atria stimulated with 10(-6) M dibutyryl cyclic isoprenaline, demonstrating that inhibition of beta-adrenergic mechanisms by thiopentone is physiologically important. Depression by thiopentone was similar in atria treated with 10(-5) M forskolin compared with preparations stimulated with 10(-6) M isoprenaline, indicating that thiopentone does not block beta-adrenergic receptors. It is concluded that thiopentone depresses myocardial function by several mechanisms, one of which involves inhibition of the adenyl cyclase cascade. The adenyl cyclase enzyme is a likely site where thiopentone inhibits the system; however, other components of the cascade may also be involved.




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Copyright © 1995 by the Canadian Anesthesiologists' Society.