The histochemical localization of cytochrome oxidase in the dentate gyrus of the rat hippocampus.

In the dentate gyrus of the rat's hippocampal formation, the activity of an oxidative enzyme, cytochrome oxidase, has been localized mostly to the molecular layer with histochemical methods that utilize diaminobenzidine. The electron microscopic localization of cytochrome oxidase indicated that mitochondria within granule cell dendrites were very reactive while those within the somata and mossy fiber terminals of this neuronal type were less reactive. Caution must be used when predicting the relative physiological activities of neurons with this method because differential activities of this enzyme occur within separate parts of the same neuronal population

Effects of neonatal monocular enucleation on the number of GAD-positive puncta in rat visual cortex.

Rats that had one eye removed on the day of birth were examined at various postnatal ages with immunocytochemical methods to determine the effect on the development of the GABAergic axonal plexus in the visual cortex. The monocular segment of visual cortex contralateral to the enucleated orbit had 20-30% fewer GABAergic axon terminals than the monocular segment of visual cortex contralateral to the normal eye. Other cortical areas did not show any significant changes. These findings suggest that sensory deprivation of the visual cortex interferes with the normal development of GABAergic neurons

Dendritic transport. II. Somatofugal movement of neuronal lysosomes induced by colchicine: evidence for a novel transport system in dendrites.

The effect of colchicine injections on the ultrastructural localization of dipeptidyl peptidase II (Dpp II) was studied in the mitral cells of the rat olfactory bulb. In control animals, electron-dense reaction product representing Dpp II activity was observed in lysosomes, lipofuscin granules, short cisternae located close to the granular endoplasmic reticulum, and dense granules. Lysosomes and lipofuscin granules were the most intensely stained organelles. Dpp II-containing organelles were localized mainly to the cell body and were randomly distributed in the perikaryal cytoplasm. Twenty-four hours after a 100-micrograms intracerebroventricular colchicine injection, the distribution of Dpp II-containing organelles was drastically altered. Short cisternae and dense granules containing Dpp II reaction product were noticeably absent in these preparations. Lysosomes and lipofuscin granules were depleted from the perikaryal cytoplasm and were concentrated in dendrites. Lysosomes were observed to extend for considerable distances in dendrites where they acquired elongated and dumbbell shapes. The shapes of some of these labeled lysosomes gave the impression that they were actively being "pulled" into the dendrites. These results indicate that microtubules sequester lysosomes to the perikaryal cytoplasm and suggest the presence of a novel transport system responsible for the movement of lysosomes from the cell body to the dendrites

Direct commissural connections to the basket cells of the hippocampal dentate gyrus: anatomical evidence for feed-forward inhibition.

After lesions were placed in the hippocampal commissures, degenerating terminals could be localized above, inside and beneath the granule cell layer of the contralateral dentate gyrus. The terminals formed asymmetric synapses with spines, dendritic shafts and somata of granule cells. Degenerating terminals also formed synapses with dendrites and somata of basket cells identified by the Golgi-electron microscope technique. These basket cells were located either at the hilar border of the granule cell layer or in the molecular layer and each formed an axonal plexus around the somata and proximal dendrites of granule cells. These observations provide an anatomical basis for the recently described feed-forward inhibition in this brain region