Intrinsic connections in the medial amygdala as revealed by complete deafferentation.

Using a newly designed knife, the medial amygdala of rats was completely deafferented to exclude the synapses of the afferents coming from the outside of the medial amygdaloid nucleus (MAN). Semiquantitative analysis by electron microscopy showed that the number of the intact dendritic synapses per unit neuropil area of the MAN of the islands was markedly reduced to about one-third of that of the controls. These intact synapses appeared to be intrinsic or of local origin. In contrast, degenerating synapses, two-thirds of the dendritic synapses in the MAN, were considered as synapses with the fibers from outside the islands.