Contribution to the amygdaloid projection field in the rat. A quantitative autoradiographic study.

Light microscopic autoradiography and quantitative photometric studies of autoradiographs were performed subsequent to injection of tritiated amino acids into various parts of the amygdala of the rat. The course of amygdalofugal fibers in the stria terminalis (bilaterally), longitudinal association bundle, medial amygdalo-hypothalamic pathway, and medial forebrain bundle is described. Evidence is provided for both additional transcapsular and paracapsular fibers and early descending stria terminalis fibers. Labeling of the ipsilateral main olfactory bulb and the bilateral acessory olfactory bulb was observed following injection into the cortical amygdaloid subnucleus. The termination of amygdalofugal fibers in the preoptic area and especially the subnucleu of the ventromedial and premamillary hypothalamic nuclei bilaterally were analysed by photometric measurement. A caudal amygdaloid projection system arises from the central amygdaloid nucleus. This system extends to the substantia nigra, lateral terminal nucleus of the accessory optic tract, central grey in the midbrain, and to the parabrachial nuclei, nucleus of the mesencephalic trigeminal tract, nucleus of the solitary tract in the hindbrain.