Nikon microscope systems utilize a variety of different bulb types depending on the microscope model and illumination type you require. The filaments and conductivity of the bulbs are specifically designed for microscopy use. This not only provides a greater evenesss of illumination but also prolongs the life of the bulb. For these reasons Nikon does not recommend non-specific bulbs.
To help you determine the bulb you need for your system, please visit Nikon's bulb selector.