Synaptic and non-synaptic immunolocalization of GABA and glutamate acid decarboxylase (GAD) in cerebellar cortex of rat.

The existence of a large number of GABA receptors in the cerebellar molecular layer, and the observation of numerous punctate immunoreactive deposits of GABA synthesizing enzyme (GAD) throughout this layer, could indicate the existence of numerous axon terminals that may be involved in neurotransmission modulated by GABA. These axon terminals may be different from those considered classically as cerebellar GABAergic axon terminals. Therefore, we have reinvestigated the localization of GABA- and GAD-immunoreactivities in the cerebellar cortex of the rat with the PAP method, using different antisera obtained from rabbits immunized with GABA, baclofen and GAD. The results observed in our investigation have demonstrated GABA- and GAD-immunoreactivities in the axon terminals considered classically as GABAergic, as well as in others which, until now, have not been considered GABAergic. This fact leads us to think that the distribution of GABA or molecules structurally similar to GABA is far more extended than previously thought in the cerebellum. We have also observed both GABA- and GAD-immunoreactivities within dendrites and glial cells. These facts suggest us a possible extrasynaptic release of GABA.

Light microscope study of the enzymatic activities of aspartate aminotransferase, GABA transaminase and acetylcholinesterase in the mesencephalic trigeminal nucleus neural complex of Mauremys caspica.

The enzymatic activities of aspartate aminotransferase, GABA-transaminase and acetylcholinesterase were studied by means of histochemical methods in the mesencephalic trigeminal nucleus (MTN) neural complex of the turtle Mauremys caspica. Light microscope observations have demonstrated that MTN neurons have a positive reaction for these enzymes.

Ultrastructural peculiarities of the supraoptic nucleus of Mauremys caspica (turtle): its evolutionary interest in reptiles.

The hypothalamic Supraoptic Nucleus (SON) supposes an evolutionary achievement in the reptiles, zoological group in which this nucleus is first differentiated. Its scarce development in the chelonian, subject of the present study, is related to their primitive brain pattern. The peculiar location and the topographical configuration of the SON in the hypothalamus of the turtle Mauremys caspica allows to evidence morphologically the successive steps in the evolutionary process from lower to higher vertebrates. The marked neurosecretory character of the chelonian SON is the unequivocal proof of its philogenetic origin derived from the magnocellular preoptic nucleus of lower vertebrates.

Ventricular labyrinths of the ependyma adjacent to the hypothalamic paraventricular nucleus in the turtle Mauremys caspica.

Labyrinthic recesses projecting to the subependymal tissue have been observed in the ependyma of the III ventricle in close relation to the neurons of the hypothalamic paraventricular nucleus in the turtle Mauremys caspica. There seems to be evidence of a direct contact between the paraventricular nucleus neurons and the cerebrospinal fluid whose physiological significance is discussed in the present work.

Altered structures in the cytoplasm of the ependymal cells next to the periventricular nucleus of the turtle Mauremys caspica.

In the apical cytoplasm of some ependymal cells of the Hypothalamic Periventricular Nucleus of the turtle Mauremys caspica large amount of cell structures of difficult diagnose are found. Their morphology is variable seeming to correspond to cell organelles in a process of degeneration, characteristic feature of the high metabolic activity in the ventricular barrier. Their possible physiological significance is discussed in the present work.

Similarity between cytoplasmic inclusions in the paraventricular hypothalamic nucleus neurons of the turtle Mauremys caspica and the cytoplasmic structures as reaction to viral infections (hepatitis) and SIDA ultrastructural tracers.

Two types of "inclusions" observed in the neurons of the hypothalamic paraventricular nucleus of the turtle Mauremys caspica, "tubular systems" and "fingerprint-like" structures, may be added to the inventory of those described in apparently normal neurons. Despite their enigmatic significance, we are inclined to think that they could be a morphological expression of viral diseases in the neuron cytoplasm. These structures have a striking similarity with those observed on pathological cells (hepatitis and SIDA).