Local administration of ETA (but not ETB) blockers into the pag area of the brain decreases blood pressure of DOCA-salt rats

The present study investigated the role possibly played by ET-receptor antagonism at periaqueductal grey (PAG) area level in decreasing the arterial blood pressure and heart rate values reached in DOCA-salt hypertensive rats. A 3-week DOCA-salt treatment induced an increase in blood pressure of up to 174+/-3 mmHg in Sprague-Dawley (SD) rats. This was paralleled by a significant increase in heart rate (HR), and endothelin-1 (ET-1) levels throughout the brain, as assessed by specific EIA ( P<0.05). In contrast, a 40% reduction of ETA mRNA levels into the brain was detected through RT-PCR. The basal MABP of DOCA rats was significantly modified by PAG injections of FR139317, an ETA receptor antagonist, or SB209670, an ETA/ETB receptor antagonist. BQ-788, an ETB receptor antagonist, was found to have no effect on blood pressure levels, while FR139317 and SB209670 also led to a significantly modified HR. PAG-endothelin ETA antagonism can therefore be said to counteract the cardiovascular changes induced by DOCA-salt treatment in rats.