Table 1.

Expression of different c-fos gene constructs injected into primary hippocampal neurons

c-fos gene construct	Stimulation	No expression (%)	Moderate expression (%)	Strong expression (%)
pFosΔCREmyc	—	91	3	6
pFosΔCREmyc	Glutamate	28	38	34
pFosΔCREΔTCFmyc	Glutamate	27	35	27
pFosΔCREΔSRFmyc	Glutamate	74	16	10

Hippocampal neurons (30–50) were injected for each construct in four independent experiments. Cells were classified as neurons on the basis of morphology and expression of neuron-specific markers. Immunofluorescence was quantified on a confocal laser scanning microscope. Cells with an immunofluorescence signal of <10%, between 10 and 40%, and >40% relative to the brightest cell in an experiment were categorized as showing no, moderate, and strong expression, respectively. Numbers indicate the percentage of the total number of neurons injected.