Related Experiment Videos
Ultrastructure of mossy fiber endings in in vitro hippocampal slices
Abstract:
0.2 to 0.4 mm thick slices of guinea pig hippocampus were studied morphologically after varying periods of incubation at 36 degrees C in Krebs-Ringer solution. Prior to fixation, the slices were tested for the presence of synaptically driven discharges of CA 3 neurons following mossy fiber (mf) stimulation because tissue preservation was satisfactory only in slices in which electrical responses were obtained. The fine structure of the MF layer in slices was compared with the ultrastructure of this region in hippocampal tissue fixed by transcardial perfusion or immersion of the tissue in the fixative. In the central part of the slices many intact neuronal structures of the mf layer could be seen even after 4 h of incubation. In the outer parts of the slices, neurons were swollen and vacuolated. These alterations were not observed in hippocampal tissue fixed by transcardial perfusion or by immersion. In all parts of the slices dark neurons and processes were found. Since dark neurons were also numerous in tissue blocks immersed in the fixative but were rare in perfused material, these changes were obviously caused by damage to unfixed tissue and fixation by immersion.
Insights
Preserving guinea pig hippocampus slices for morphological study requires careful fixation. Electrical activity testing ensures tissue viability, revealing that incubation degrades outer layers while inner layers remain intact.
Area of Science:
- Neuroscience
- Cell Biology
- Histology
Background:
- Studying neuronal morphology in brain slices is crucial for understanding neural circuits.
- Maintaining cellular integrity during slice preparation and incubation is a significant challenge.
- Hippocampal CA3 neurons and mossy fiber pathways are key components of memory formation.
Purpose of the Study:
- To evaluate the morphological preservation of guinea pig hippocampal slices after incubation.
- To compare slice fixation methods with traditional perfusion and immersion techniques.
- To identify factors affecting neuronal structure in incubated hippocampal tissue.
Main Methods:
- Preparation of 0.2-0.4 mm thick guinea pig hippocampal slices.
- Incubation at 36°C in Krebs-Ringer solution for varying durations.
- Electrical stimulation of mossy fibers to assess neuronal activity and tissue viability.
- Morphological analysis using electron microscopy, comparing slices with transcardial perfusion and immersion fixation.
Main Results:
- Central regions of incubated slices showed intact neuronal structures up to 4 hours.
- Outer regions of incubated slices exhibited neuronal swelling and vacuolation.
- Dark neurons and processes were observed in all parts of incubated slices.
- Dark neuron prevalence correlated with immersion fixation and unfixed tissue damage, unlike perfusion-fixed tissue.
Conclusions:
- Incubation of hippocampal slices leads to differential morphological degradation, affecting outer layers more severely.
- Electrical activity assessment is a reliable indicator of tissue viability for morphological studies.
- Transcardial perfusion is superior to immersion for preserving hippocampal ultrastructure, minimizing artifactual changes like dark neurons.