CARDIOVASCULAR EFFECTS OF NEURONAL ACTIVATION OF THE EXTENDED AMYGDALA IN RATS

The bed nucleus of the stria terminalis (BST) and the sublenticular su bstantia innominata (SI) are considered rostral extensions of the medi al and central amygdaloid nuclei. In contrast to amygdaloid nuclei pro per, the involvement of BST and SI neurons in cardiovascular control h as not been studied. These areas were systematically explored in 35 ur ethane-anesthetized Wistar rats for sites from which changes in arteri al 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 response s were elicited from only 3 sites; 43 sites were not responsive. An ad ditional group of 10 rats was instrumented for bilateral Glu injection s (0.1 M, 200 nl per side) into the ventral division of the lateral BS T and ventral BST and for the recording of AP, HR and regional blood f lows measured with pulsed Doppler probes in the conscious state. In th ese rats, decreases in AP (- 11.9 +/- 1.7 mmHg) were accompanied by si gnificant increases in hindquarter conductance (44.2 +/- 11.4%), while renal and mesenteric vascular conductances remained unchanged. The fa ll 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 overal l central control of the circulation remains to be established.