Substance P in the amygdaloid complex, bed nucleus and stria terminalis of the rat brain.

Radioimmunoassay and immunohistochemical techniques have demonstrated the presence of substance P in the medial and central nuclei of the amygdala and the bed nucleus of the stria terminalis. Hemisections and micro-knife cuts transecting the anterior, posterior, medial, lateral and ventral connections to the amygdala did not modify the content of substance P in the amygdala. In addition knife cuts totally isolating the medial amygdaloid nucleus from lateral and anterior-posterior connections did not reduce the substance P content of the medial nucleus, but produced a 70% reduction in the substance P content of the central nucleus. These results suggest that substance P containing neurones in the medial and central amygdaloid nuclei do not receive substance P projections originating outside the amygdala. However, there appears to be a short substance P projection from the medial nucleus to the central nucleus.