Synapsoarchitectonics of the septum of the cat brain

In the medial and lateral septal nuclei, 4 types of axonal terminals are distinguished. Type I contains spherical vesicles and forms asymmetric synapses on small and middle stems and spines of the dendrites; type I terminals comprise 63% in the medial nucleus of the total number of axons, and in the lateral one--52%. Type II contains polymorphic vesicles and forms symmetrical synapses on the soma and large dendrites. In the medial nucleus they comprise 6%, and in the lateral one--3%. Type III contains either clear spherical (IIIa), or polymorphic (IIIb) vesicles, as well as 1-2 vesicles with a dense core. They form axodendritic, axospine and axosomatic synapses. In the medial nucleus they comprise 25% and 3%, respectively, in the lateral one--40% and 2%. Type IV contains a great number of vesicles with a dense core. These terminals in both septal nuclei comprise 3% and do not participate in formation of active contacts.