4.1.5. Cell Viability Assessment—MTT Assay

Both neurons and astrocytes were exposed to serial dilutions of C11 (100, 500, 1000, and 2500 ng/mL) used alone or in combination with 3-mM glutamate. Solutions of the investigated compound were prepared in the culture medium suitable for given cells (as described above). In the case of experiments performed in conditions of trophic stress, solutions of C11 were prepared in the medium deprived of B-27 supplement (neurons) or the medium with reduced to 2% of FBS (astrocytes). Metabolic activity of nerve cells in the response to C11 was examined after 48 h of treatment using the MTT assay. In order to properly interpret the obtained results before the addition of MTT, all plates were checked under the light microscope, and afterward, the MTT solution (5 mg/mL in phosphate-buffered saline, PBS) was added for 3 h. Resultant crystals were solubilized overnight in SDS buffer pH 7.4 (10% SDS in 0.01 N HCl) and the product quantified spectrophotometrically by measuring the absorbance at a 570-nm wavelength using a microplate reader (BioTek ELx800, Highland Park, Winooski, VT, USA). The results were presented as a percentage of cell viability treated with the investigated compounds versus cells grown in the control medium (indicated as 100%).