Organization of projections from the juxtacapsular nucleus of the BST: a PHAL study in the rat.

The axonal projections of the juxtacapsular nucleus of the anterior division of the bed nuclei of the stria terminalis (BSTju) were examined with the Phaseolus vulgaris-leucoagglutinin (PHAL) method in the adult male rat. Our results indicate that the BSTju displays a relatively simple projection pattern. First, it densely innervates the medial central amygdalar nucleus and the subcommissural zone and caudal anterolateral area of the BST - cell groups involved in visceromotor responses. Second, it provides inputs to the ventromedial caudoputamen (CP) and anterior basolateral amygdalar nucleus - areas presumably modulating somatomotor outflow. Third, the BSTju sends dense projections to the caudal substantia innominata, a distinct caudal dorsolateral region of the compact part of the substantia nigra, and the adjacent mesencephalic reticular nucleus and retrorubral area. And fourth, the BSTju provides light inputs to the prelimbic, infralimbic, and ventral CA1 cortical areas; to the posterior basolateral, posterior basomedial, and lateral amygdalar nuclei; to the paraventricular and medial mediodorsal thalamic nuclei; to the subthalamic and parasubthalamic nuclei of the hypothalamus; and to the ventrolateral periaqueductal gray. These projections, in part, suggest a role for the BSTju in circuitry integrating autonomic responses with somatomotor activity in adaptive behaviors.