The bed nucleus of the stria terminalis (BST) and the sublenticular substantia innominata (SI) are considered rostral extensions of the medical and central amygdaloid nuclei. In contrast to amygdaloid nuclei proper, the involvement of BST and SI neurons in cardiovascular control has not been studied. These areas were systematically explored in 35 urethane-anesthetized Wistar rats for sites from which changes in arterial pressure (AP) and heart rate (HR) could be obtained by injection of 20 nl of glutamate solutions (Glu, 0.5 M). Injections into 84 of the 130 histologically verified sites were followed after an 8.0 +/- 0.7 s latency by depressor responses ranging from -4 to -33 (mean -13.3 +/- 0.8) mmHg, accompanied by variable changes in HR. Pressor responses were elicited from only 3 sites; 43 sites were not responsive. An additional group of 10 rats was instrumented for bilateral Glu injections (0.1 M, 200 nl per side) into the ventral division of the lateral BST and ventral BST and for the recording of AP, HR and regional blood flows measured with pulsed Doppler probes in the conscious state. In these rats, decreases in AP (-11.9 +/- 1.7 mmHg) were accompanied by significant increases in hindquarter conductance (44.2 +/- 11.4%), while renal and mesenteric vascular conductances remained unchanged. The fall in AP usually preceded the rise in hindquarter flow. These results suggest the existence of a depressor area in regions of the BST and SI, but the contribution of the elicited depressor effects in the overall central control of the circulation remains to be established.