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The localization of metabotropic glutamate receptors of groups II (mGluR2/3) and III (mGluR4a) and the subunits 2 and 3 of alfa-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) ionotropic glutamate receptors (GluR2/3) was investigated with immunocytochemical methods in the rat adrenal gland. MGluR2/3, mGluR4a and GluR2/3 immunoreactivities were observed in large-sized, centrally located type I adrenal medullary ganglion neurons. Furthermore, the small-sized type II adrenal ganglion neurons identified by their immunoreactivity to brain nitric oxide synthase (bNOS), also expressed mGluR2/3, mGluR4a and GluR2/3. These cells were disposed in the peripheral portion of the adrenal medulla. None of the type I neurons were positively labeled for bNOS. These morphological observations suggest that activation of glutamate receptors in ganglion neurons may be instrumental in the control of adrenal endocrine systems as well as blood regulation.

Injections of the low diffusion retrograde tracer rhodamine latex microspheres were made in the pontine grey matter of the cat in order to study the cortical convergence to the pons. We found a different distribution of cells in the convex surface of the brain hemisphere making ventral or dorsolateral injections. In the first case, cells were grouped in the top of the gyri. In the second case, cells were more frequent in the bottom of the sulci. Our results show a possible retinotopic organization of this projection.

The characteristics and distribution pattern of retinal afferent terminals making synaptic contacts on narrow field vertical neurons in the stratum griseum superficiale of the rabbit superior colliculus were studied using the Golgi-gold substitution technique in combination with either autoradiographic or degenerative methods. At the level of light microscopy, identified gold-toned vertical neurons showed similar features to those previously described by others. Although their axons were frequently seen rising from the basal dendritic tuft, they could also emerge from an apical dendrite, but rarely from the cell body. The electron microscopic study revealed that these neurons received radiolabelled or degenerated profiles with typical features of retinal terminals, while more proximal parts seemed to receive fewer terminals but of larger size. Axo-somatic synaptic junctions were very rare and, interestingly, retinal terminals were not seen forming synapses on the basal dendritic arborization. The present results indicate that the narrow field vertical cells are targets for retinotectal projection.