Comparative histochemical study of the nuclei of the specific systems and reticular formation of the brain in a series of mammals

Summary

Histochemical methods were used to study the comparative distribution of succinate dehydrogenase (SDH) and acetylcholinesterase (ACE) activity in the reticular formation nuclei of the predulla and in the “specific” formation of the medulla and the nuclei of Goll and Burdach in the spinal cord, the nucleus of the hypoglonal nerve and the motor nuclei of the spinal cord in mammals with a different complexity of organization of the nervous system. The activity of SDH and ACE differed in the representatives of various orders of mammals. It decreased in the series: hedgehog, rat, cat, monkey. The nuclei of the “specific” brain formations chiefly possessed higher enzymatic activity than the reticular nuclei and the activity distribution in them was the same in all the animals. In the reticular nuclei changes occurred in the correlation of the activity level between the neuron bodies and “intercellular” structures compared with the hedgehog, in other animals the activity in the nerve cell bodies fell to the level of enzyme activity in the structures surrounding the cells. A gradual division of reticular formations into lateral and medial areas becomes evident; the SDH activity was higher in the medial area structures. This process is evidently connected with the functional differentiation of the reticular formation of the medulla during evolution.