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PubMed1999

[The effects cervicothoracic sympathetic blockade on left ventricular function].

OBJECTIVE: Cervicothoracic sympathetic blocks (stellate ganglion blocks) not only influence pain, but also lead to regional sympathetic denervation of part of the left ventricular wall, while other ventricular regions stay under the control of the unblocked side. What is the influence of these imbalances of sympathetic innervation on ventricular function? METHODS: Thirteen anaesthetised dogs were instrumented for measurement of left ventricular pressure (tip-manometer), cardiac output (ultrasonic flow probe) and regional myocardial function (sonomicrometry) in two left ventricular regions, innervated by the left or right sympathetic system, respectively. Electrical stimulations of the left and right stellate ganglia, and left and right sided stellate ganglion blocks were performed. In eight patients with no cardiac disease, the effects of left stellate ganglion blocks on echocardiographic variables of ventricular function were investigated. RESULTS: In dogs, the unilateral ganglion stimulations led to an increase in regional and global contractility. However, left ventricular wall motion became asynchronous and, despite an increase in contractility, relaxation was impaired. After the ganglion blocks, there was a decrease in regional contractility within the denervated area, also leading to an asynchronous wall motion. As a consequence, relaxation was impaired, but cardiac output was maintained. In the patients, there was an increase in isovolumic relaxation time. This change was also within the compensatory range and cardiac output increased slightly as a consequence of a simultaneous afterload reduction by the ganglion block. CONCLUSION: The studies show a disturbance of diastolic function after stellate ganglion blocks, resulting from an asynchronous wall motion pattern after the regional denervation. However, the changes were within the compensatory range of a healthy ventricle and cardiac output was not reduced.

Anesthesia, Spinal↗
PubMed1997

Preferential inhibition of Ih in rat trigeminal ganglion neurons by an organic blocker.

The potency and specificity of a novel organic Ih current blocker DK-AH 268 (DK, Boehringer) was studied in cultured rat trigeminal ganglion neurons using whole-cell patch-clamp recording techniques. In neurons current-clamped at the resting potential, the application of 10 microM DK caused a slight hyperpolarization of the membrane potential and a small increase in the threshold for action potential discharge without any major change in the shape of the action potential. In voltage-clamped neurons, DK caused a reduction of a hyperpolarization-activated current. Current subtraction protocols revealed that the time-dependent, hyperpolarization-activated currents blocked by 10 microM DK or external Cs+ (3 mM) had virtually identical activation properties, suggesting that DK and Cs+ caused blockade of the same current, namely Ih. The block of Ih by DK was dose-dependent. At the intermediate and higher concentrations of DK (10 and 100 microM) a decrease in specificity was observed so that time-independent, inwardly rectifying and noninactivating, voltage-gated outward potassium currents were also reduced by DK but to a much lesser extent than the time-dependent, hyperpolarization-activated currents. Blockade of the time-dependent, hyperpolarization-activated currents by DK appeared to be use-dependent since it required hyperpolarization for the effect to take place. Relief of DK block was also aided by membrane hyperpolarization. Since both the time-dependent current blocked by DK and the Cs+-sensitive time-dependent current behaved as Ih, we conclude that 10 microM DK can preferentially reduce Ih without a major effect on other potassium currents. Thus, DK may be a useful agent in the investigation of the function of Ih in neurons.

Action Potentials↗