Neurovascular function during pregnancy in the spontaneously hypertensive rat.

1. Blood pressure (BP) declines dramatically in the final week of gestation in the pregnant spontaneously hypertensive rat (SHR). This study investigated the hypothesis that alterations of vascular neuroeffector function in the pregnant SHR and normotensive Wistar-Kyoto (WKY) rat are responsible for this decline. 2. Pregnancy in SHR and WKY rats was associated with a significant drop in BP in the last week of gestation. 3. Responses of the perfused mesenteric vasculature to bolus doses of noradrenaline (NA) and potassium chloride (KCl) were decreased in preparations from SHR rats 4 days before delivery. This decreased responsiveness was absent in preparations from SHR rats 1 day before delivery. Responses of the perfused mesenteric vasculature to sympathetic nerve stimulation were not influenced by pregnancy in the SHR. 4. It is concluded that while there are dynamic changes occurring in neurovascular function just prior to delivery, it is unlikely that they are wholly responsible for the dramatic decline in blood pressure in the SHR rat.