THE HYPOTHALAMIC AGGRESSION REGION OF THE RAT OBSERVATIONS ON THE SYNAPTIC ORGANIZATION

Comparison of detailed physiological and morphological data shows that the hypothalamic aggression region in the rat largely coincides with the intermediate hypothalamic area. This region has a neuronal density of about 35.10(3) neurons per mm3, a synaptic density of about 300.10(6) per mm, and a synapse to neuron ratio of about 9000, including only about 200 axosomatic synaptic contacts per neuron. Septal synaptic contacts in this region originate from unmyelinated axons and are axodendritic of the asymmetrical type, with an average bouton diameter of 785 nm and an average synaptic contact length of 270 nm.