Fine structure and synaptic connections of identified neurons in the rat fascia dentata

Abstract

A survey is given of the synaptic connections of identified neurons in the rat fascia dentata based on our own Golgi/electron microscopic and light and electron microscopic immunocytochemical findings as well as on results obtained from the literature. The report largely deals with the dominating cell type in the region, the dentate granule cell. Of the various types of hilar cells, the GABAergic neurons, particularly the inhibitory basket cells, are taken into account. Differences in fine structure between granule cells and basket cells as well as mutual synaptic connections between these two types of dentate neurons are elaborated. This survey may provide a basis for further neurophysiological and pharmacological studies on these cells.

Muscarinic amplification of fast excitation in hilar neurones and inhibition in granule cells in the guinea‐pig hippocampus.

“…This difference in synaptic activation of hilar neurones and granule cells is attributable to their synaptic connectivity. In the hippocampal-slice preparation, in which the entorhinal cortex is not included, hilar neurones receive multiple excitatory inputs from intrinsic neurones (Lubbers & Frotscher, 1987;Scharfman et at. 1990;Muller & Misgeld, 1991), while granule cells receive predominantly inhibitory synapses from neurones (Lubbers & Frotscher, 1987;Han, Buhl, L6rinczi & Somogyi, 1993) which can be expected to be preserved in the slice (Fig.…”

Ectopic Granule Cells of the Rat Dentate Gyrus

“…The soma size and shape, asymmetric or 'polarized' dendritic tree, and mossy fiber axon are useful attributes, as are dendritic spines, and these were used by Marti-Subirana et al [1986] to define granule cells. In addition, the granule cell has characteristic ultrastructural features [Lübbers and Frotscher, 1987;. However, there is some variability in these features even in the granule cells located in the granule cell layer.…”

Coexistence of muscarinic acetylcholine receptors and somatostatin in nonpyramidal neurons of the rat dorsal hippocampus

“…In addition, a subclass of the cholinergitally innervated nonpyr~d~ neurons in the hilar re.gion of the dentate gyms was proven to be SOMergic in nature (27,29). In agreement with these observations, we recently demonstrated a monosynaptic septal input to SOMergic hippocampal neurons by P~use~l~s vulgar-is leuco-agglutinin (PHA-L) tracing (51).…”

“…It is concluded that these SOMergic cells serve both feed-forward and feed-back inhibitory processes in the dentate gyrus (1 I ,29). Furthermore, cholinergic afferents to GABAergic hilar basket cells are implicated in feed-forward inhibition (28,29). Taken together, the SOMergic muscarinic cholinoceptive neurons found in this study are likely candidates for inhibitory processes driven by the excitatory cholinergic septal input.…”