Role of L-type Ca2 + channels, sarcoplasmic reticulum and Rho kinase in rat basilar artery contractile properties in a new model of subarachnoid hemorrhage

We have previously described that L-type Ca2 + channels' (LTCCs) activation and metabotropic Ca2 + release from the sarcoplasmic reticulum (SR) regulate RhoA/Rho kinase (ROCK) activity and sustained arterial contraction. We have investigated whether this signaling pathway can be altered in a new experimental model of subarachnoid hemorrhage (SAH). For this purpose, arterial reactivity was evaluated on days 1 to 5 after surgery. A significant increase of basal tone, measured 4 and 60 min after normalization, was observed on day 5 after SAH and at 60 min on days 2 and 3 after SAH. This phenomenon was suppressed with LTCCs and ROCK inhibitors. We have also studied arterial rings vasoreactivity in response to high K+ solutions. Interestingly, there were no significant differences in the phasic component of the high K+-induced contraction between sham and SAH groups, whereas a significant increase in the sustained contraction was observed on day 5 after SAH. This latter component was sensitive to fasudil, and selectively reduced by low nifedipine concentration, and phospholipase C and SR-ATPase inhibitors. Therefore, our data suggest that the metabotropic function of LTCCs is potentiated in SAH. Our results could provide a new strategy to optimize the pharmacological treatment of this pathological process.

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