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In the lateral hypothalamus, groups of functionally related cells tend to be widely scattered rather than confined to discrete, anatomically distinct units. However, by using parvalbumin (PV)-specific antibodies, a solitary, compact cord of PV-immunoreactive cells (the PV1-nucleus) has been identified in the ventrolateral tuberal hypothalamus in various species. Here we describe the topography, the chemo-, cyto-, and myeloarchitectonics, and the ultrastructure of this PV1-nucleus in rodents. The PV1-nucleus is located within the ventrolateral division of the medial forebrain bundle. In the horizontal plane, it has a length of 1 mm in mice and 2 mm in rats. PV-immunoreactive perikarya fall into two distinct size categories and number (~800 in rats and ~400 in mice). They are intermingled with PV-negative neurons and coarse axons of the medial forebrain bundle, some of which are PV-positive. Symmetric and asymmetric synapses, as well as PV-positive and PV-negative fiber endings, terminate on the perikarya of both PV-positive and PV-negative neurons. PV-positive neurons of the PV1-nucleus express glutamate, not γ-aminobutyric acid (GABA), the neurotransmitter that is usually associated with PV-containing nerve cells. Although we could not find evidence that PV1 neurons express either catecholamines or known neuropeptides, they sometimes are interspersed with the fibers and terminals of such cells. From its analogous topographical situation, the PV1-nucleus could correspond to the lateral tuberal nucleus in humans. We anticipate that the presence of the marker protein PV in the PV1-nucleus of the rodent hypothalamus will facilitate future studies relating to the connectivity, transcriptomics, and function of this entity., (Copyright © 2011 Wiley Periodicals, Inc.)

The qualitative and quantitative distribution pattern of hyaluronan (HA), a component of the extracellular matrix (ECM), was studied in the frog central nervous system by using a highly specific HA probe and digital image analysis. HA reaction was observed in both the white and the gray matter, showing a very intense staining around the perikarya and dendrites in the perineuronal net (PN). In the telencephalon, strong reaction was found in different parts of the olfactory system, in the pallium, and in the amygdala. In the diencephalon, intensive staining was found in the nucleus of Bellonci, the dorsal habenula, the lateral and central thalamic nuclei, and the subependymal zone of the third ventricle. In the mesencephalon, layers of optic tectum displayed different intensities, with the strongest reaction in layers B, D, F, 3, and 5. Other structures of the mesencephalon showed regional differences. The PN was especially intensively stained around the perikarya of the toral nuclei, the oculomotor and trochlear nuclei, and the basal optic nucleus. In the rhombencephalon, the granular layer of cerebellum, the vestibulocochlear nuclei, the superior olive, the spinal tract of the trigeminal nerve, and parts of the reticular formation showed the most intense reaction in the PN. In the spinal cord, considerable HA staining was found in the white matter and around the perikarya of motoneurons. The present study is the first description of the HA-positive areas of frog brain and spinal cord demonstrating the heterogeneity of HA distribution in the frog central nervous system., (Copyright 2006 Wiley-Liss, Inc.)