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The aspartate aminotransferase activity (AAT) is reserched into the spinal cord, the medulla oblongata and the cerebellar nuclei of the rat, chicken, Lacerta lepida and Bufo calamitas. It's proved that the AAT activity shows in many locations, that are mainly: 1. In the nerve fibers 2. In the cytoplasmic membrane, and in the nuclear membrane of the neurons 3. In all neuronal cytoplasm, and 4. In the mitochondria of neurons and choroid plexus cells. The results base the idea that there's more than one pool of glutamic acid in relation to that AAT. It's suggested that the role that AAT plays is different in everyone of the described locations, and may be it's connected with transport phenomenons in the membrane, with energetic function on the mitochondria and with functions of the nerve impulse transmission in the synapsis. We remark, finally, the interest that the enzymatical works can have the time comming to establish homologies among similar structures of several animal's nervous system.

In many cases, in a fixed neuronal circuit, the complete morphological and biochemical development of a neuron depends on the impulses it receives from the neuron before. The possible involvement of this phenomenon to learning is studied in this work.

In this work we research into the GDH location of the spinal cord, in the medullar oblongata and in the central cerebellar nuclei of the rat, cat, dog, chicken, lizard (Lacerta lepida), and Toad (Bufo calamita). The GDH is located at the cytoplasm and at the neuronal prolongations, at oligodendrocytes cells, at Lecerta ependimary glial cells, and at the capillary walls.

In this work is studied the tannin-iron method specificity when the ferrous chloride is replaced by other iron compounds. Nervous tissue and rat duodenum cuts are used. Cuts were treated with tannic acid and after with FeCl3; FeCl2; FeOHCl2; FeAc2; Fe2O3; FeSO4; NH4Fe(SO4)2 or colloidal iron solution. Dilution effect from every one of aforementioned iron compounds too is studied. The obtained results with those furnished by the OTA method by using the tannic acid in identical conditions are compared. Also several treatments of blockade were carried-out. The obtained results prove that iron ions play a different role in the mucins staining than in other demonstrable substances coloration in the nervous tissue. In the same way evidences that the iron ion that joins the mucins in the tannin-iron method is the FeOH++ ion were obtained.

Union of several iron compounds and other metallic cations to the duodenum mucines and to the neuronal surface mucopolysaccharides is studied. The results differentiate clearly the behaviour of the duodenum mucosubstances and neuronal surface mucosubstances. The duodenum mucines only attract to certain cations, in such a way that their union seems to be specific. On the contrary the neuronal surface mucopolysaccharides attract to most of the assaied metallic cations. These results coincide with other biochemical ones that prove that cationic attraction by the acid mucopolysaccharides is of electrostatic nature. To reveal the metallic cation union to the mucopolysaccharides is used ammonium sulphide in solution. The physiological role of these perineuronal mucopolysaccharides in relation to nervous impulse transmission and propagation is discussed attending to the obtained results.

A histochemical study on Lacerta lepida cerebral cortex glutamic dehydrogenase activity (GLD) was reported in this paper. The GLD activity is revealed in neurons and fibers of cerebral cortex. The regions M1 and M2 were differentiated with regard to enzymatical activity. The M2 neurons are morphologically and histochemically similar to D1 neurons but not to M1 neurons.