Which stain is specifically used for astrocytes, resulting in a black appearance on a light brownish background?

The stain that is specifically used for astrocytes and results in a black appearance on a light brownish background is Cajal's gold sublimate. This unique staining method selectively targets neuroglial cells, particularly astrocytes, allowing for the detailed visualization of their morphology within nervous tissue. The distinctive black coloration represents the astrocytes, whereas the lighter brown background corresponds to other cellular components and structural elements in the tissue.

Hematoxylin and eosin stain, while commonly used in histopathology, does not specifically highlight astrocytes in the same manner or provide the same level of specific differentiation in color. Masson's trichrome stain is generally used to differentiate between collagen and muscle fibers rather than specifically highlighting astrocytes. Giemsa stain is often used for blood and bone marrow analyses, primarily focusing on cellular components rather than specific cellular types like astrocytes.

In summary, Cajal's gold sublimate is prized for its specificity in staining astrocytes, making it the correct choice for identifying these cells in histological preparations.