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Rolle der Kaliumkanäle und des cGMP bei der Dilatation der perfundierten A. cerebri media der Ratte auf Azidose

perivascular nerves modulates cerebral arteriolar pH reactivity. extraluminal acidosis occurs via combined activation of ATP-sensitive and Ca 2+-activated potassium channels. Abstract Acidosis is one of the most potent vasodilators in the cerebral circulation. Although first described 1890 by Roy and Sherrington the mechanisms of vasodilation to acidosis are still unknown. Experimental data show, that nitric oxide (NO) is a modulator but not a mediator of cerebral arterial pH reactivity. NO also acts as a modulator of neurovascular coupling in the rat somatosensory cortex. We used the experimental in vitro model of the isolated and perfused middle cerebral artery (MCA) to elucidate the general mechanisms of NO-modulated dilations. The present study was performed to clarify the role of cGMP and potassium channels for mediation of acidosis-induced dilation of cerebral arteries. The results indicate, that vasodilation to acidosis is mediated by cGMP. Restoring the basal cGMP-level we could demonstrate a permissive role of cGMP in the vasodilation to acidosis. We could also show that K Ca are active under resting conditions and are able to contribute to the relaxation of the MCA to acidosis. Other potassium channels like K ATP , K ir , K V and the Na + /K + ATPase appeared not to be involved in the process of dilation to acidosis. After administration of a selective inhibitor of K ATP in addition to an inhibitor of K Ca the relaxation to acidosis was completely abolished. Simultaneous application of selective inhibitors of K ATP and BK Ca also prevented from vasodilation to acidosis. These results indicate, that relaxation to acidosis is mediated by activation of K ATP and BK Ca. This potassium channels seem to have a redundant activity, in such a way that K Ca could substitute for K ATP. The present findings are a starting point for further studies concerning the modulation of K ATP and BK Ca by the NO/cGMP-System. This studies are a basis for coming experiments to determine the role of K ATP and BK Ca in the neurovascular coupling.