Regional distribution of choline acetyltransferase and acetylcholinesterase within the amygdaloid complex and stria terminalis system

The distribution of "marker" enzymes for cholinergic neurons has been studied in 10 subdivisions of the amygdaloid complex of the rat brain. Choline acetyltransferase activity was measured using a radiochemical method in samples dissected from fresh serial sections. Acetylcholinesterase was studied using a histochemical procedure. Both enzymes had similar patterns of distribution within the amygdaloid complex and were most concentrated in the posterior lateral and basolateral nuclei and in the nucleus of the lateral olfactory tract. These enzymes were much less concentrated in the cortical, medial, central, and basomedial nuclei. Large differences in acetylcholinesterase staining were found within the lateral posterior and the basolateral nuclei and within the pyriform cortex. Biochemical studies showed a parallel distribution of choline acetyltransferase within these nuclei. The results indicate that cholinergic neural elements in the amygdala are concentrated primarily in the basolateral complex and suggest that this region may be innervated by cholinergic fibers traveling in the ventral amygdalo-fugal pathway.