Amygdaloid efferents through the stria terminalis in the rat give origin to zinc‐containing boutons

Abstract

Many regions of the basal forebrain are innervated by zinc‐containing axonal boutons. In the present work, the lesion/degeneration method, coupled with histochemical staining for zinc‐containing boutons, was used to determine the origins and efferent pathways of these zinc‐containing projections to the basal forebrain. Knife cuts of the stria terminalis or extensive electrolytic lesions of the amygdala resulted in the bleaching of the staining for zinc (Timm stain) and terminal degeneration (Fink‐Heimer method) ipsilaterally in the following areas: granule cell layer of the accessory olfactory bulb, shell of nucleus accumbens, bed nucleus of the stria terminalis, striohypothalamic nucleus, retrochiasmatic area, ventromedial hypothalamic nucleus (in the cell‐sparse shell), medial tuberal nucleus, terete hypothalamic nucleus, and ventral premammillary nucleus. Small lesions made with ibotenic acid in the posteromedial part of the amygdalohippocampal area caused bleaching of the stain for zinc in the accessory olfactory bulb, in the medial zone of the bed nucleus of the stria terminalis, and in the ventral premammillary nucleus. Lesions in either the ventral subiculum or the anterolateral part of the amygdalohippocampal area caused bleaching in the ventromedial hypothalamic nucleus. Lesions in the hippocampus or in the neocortex did not produce bleaching of the stain for zinc in the above‐mentioned terminal fields. The present results agree with previous studies on amygdaloid efferents and suggest that neurons in the amygdalhippocampal area and, possibly, in the ventral subiculum give origin to zinc‐containing boutons.