The hilus (also called the polymorphic layer) of the dentate gyrus is a critically important region of the hippocampal formation that contains a diverse population of neurons essential for proper hippocampal circuit function. Located between the granule cell layer and the CA3 region, the hilus houses both excitatory mossy cells and various inhibitory interneurons that collectively modulate dentate gyrus activity and support hippocampal-dependent learning and memory [1]. This comprehensive guide covers the cellular composition, physiological functions, and involvement of hilar neurons in neurodegenerative diseases including Alzheimer's disease (AD) and temporal lobe epilepsy. [1]
| Property | Value | [2]
|----------|-------| [3]
| Category | Dentate Gyrus, Hippocampal Formation | [4]
| Location | Polymorphic layer of dentate gyrus, between granule cell layer and CA3 | [5]
| Cell Types | Mossy cells, HIPP cells, SOM+ interneurons, HDC cells, astrocytes | [6]
| Primary Neurotransmitters | Glutamate (mossy cells), GABA (interneurons) | [7]
| Key Markers | Calretinin, NPY, Somatostatin, ZnT3 (zinc), mGluR1α |
| Volume (human) | ~1-2 mm³ |
| Taxonomy | ID | Name / Label |
|---|---|---|
| Cell Ontology (CL) | CL:0002095 | hilus cell of ovary |
The hilus is situated in the dentate gyrus:
The hilus contains diverse neuronal populations:
| Cell Type | Marker | Target | Function |
|---|---|---|---|
| HIPP cells | Somatostatin, NPY | Molecular layer interneurons | Feedback inhibition |
| HDC cells | Calretinin | Granule cell bodies | Feedforward inhibition |
| Ivy cells | NPY, PV | Granule cells | Sustained inhibition |
| MOP cells | MOP | Granule cells | Modulation |
Mossy cells are the primary excitatory neurons in the hilus:
Hilar interneurons provide inhibitory modulation:
Entorhinal Cortex (Layer II) → Perforant Path → Granule Cells
↓
Mossy Fibers → CA3 Pyramidal Cells
↓
Mossy Cells ← Feedback ←
↓
Hilar Interneurons ←
↓
Modulate Granule Cells
The hilus is a hub in the hippocampal circuit:
The dentate gyrus performs pattern separation:
Hilar neurons support consolidation:
The hilus contains neural progenitor cells:
Hilar neurons are significantly affected in AD:
Hilar neurons are critically involved in epilepsy:
Hilar involvement in PD:
| Condition | Hilar Involvement | Clinical Relevance |
|---|---|---|
| Schizophrenia | Altered inhibition | Cognitive deficits |
| PTSD | Mossy cell changes | Memory dysfunction |
| Normal aging | Moderate cell loss | Age-related memory decline |
The study of Hilar Neurons (Dentate Gyrus) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
Sloviter RS. Permanently altered hippocampal structure, excitability, and inhibition after experimental status epilepticus in the rat: the "dormant basket cell" hypothesis and its possible relevance to temporal lobe epilepsy. Hippocampus. 1991;1(1):41-66. 1991. ↩︎
Scharfman HE. The role of mossy cells in epileptogenesis. J Clin Neurophysiol. 2007;24(4):301-308. 2007. ↩︎
Spalding A, Berglas J, Jones V, et al. Mossy cells in Alzheimer's disease exhibit early loss and tau pathology. Neurobiol Aging. 2020;95:134-144. 2020. ↩︎
[Amaral DG, Scharfman HE, Lavenex P. The dentate gyrus: fundamental neuroanatomical organization (dentate gyrus for dummies). Prog Brain Res. 2007;163:3-22](https://doi.org/10.1016/S0079-6123(07). 2007. ↩︎
Scharfman HE, Myers CE. Hilar mossy cells of the dentate gyrus: a historical perspective. Neural Plast. 2012;2012:972456. 2012. ↩︎
Jinde S, Zapporetti S, Parent M, et al. Hilar mossy cell degeneration causes transient dentate granule cell hyperexcitability and impaired pattern separation. Neuron. 2012;76(6):1189-1200. 2012. ↩︎
[Freund TF, Buzsáki G. Interneurons of the hippocampus. Hippocampus. 1996;6(4):347-470](https://doi.org/10.1002/(SICI). 1996. ↩︎