engleski

Morphological Analysis of Hippocampal Neurons in Green Fluorescent Protein-Expressing Transgenic Mice

Mice expressing green fluorescent protein (GFP) in a small percentage of neurons in the brain are a useful tool to study basic principles of neuroanatomy on the level of single cells. In a recently described mouse strain (GFP-M ; Feng et al. [2000], Neuron 28:41-51), GFP is expressed in a small subset of neurons under the control of the neuron-specific Thy-1 promoter. These neurons exhibit a Golgi-like labeling of the entire cell. To use this mouse for studies on neuronal plasticity in the hippocampus, the basic distribution pattern of GFP-positive neurons as well as their cellular characteristics were analyzed. First, the types of cells expressing GFP were identified and selected cells were three-dimensionally reconstructed using confocal image stacks (Neurolucida system). The majority of cells expressing GFP were hippocampal principal cells (granule cells as well as CA3 and CA1 pyramidal neurons). Using confocal double-immunofluorescence against calbindin, calretinin and parvalbumin, mossy cells located in the hilus of the dentate gyrus could also be identified as GFP-expressing neurons. No other type of hippocampal neuron appeared to be GFP-positive. Second, serial sections of the hippocampus were used to map the distribution of the various types of GFP-positive cells along the septo-temporal axis of the hippocampus. Whereas the number of GFP-positive pyramidal cells increased from the septal to the temporal pole of the hippocampus, GFP-positive granule cells were more numerous in the septal region. GFP-positive mossy cells were restricted to the temporal region of the hippocampus. Since the axons of GFP-expressing cells were also labeled, the mossy fiber projection, the mossy cell axon termination zone in the inner molecular layer, and the commissural/associational collaterals of the pyramidal cell axons in stratum radiatum could also be identified within the hippocampus. These data provide an anatomical baseline for future studies on neuronal plasticity in the hippocampus.

hippocampal neurons; 3D reconstruction; EGFP-transgenic mice

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