Datura stramonium lectin staining of glial associated extracellular material in insect brains.

To investigate how glial cells structure the neuropile of olfactory pathways in the brains of honeybees and locusts, we used a lectin as a carbohydrate specific molecular label. On frozen sections, Datura stramonium lectin (DSL) stained extracellular material which is mainly associated with glial cells. Preadsorption of the DSL with the carbohydrate N, N'-diacetylchitobiose blocked the staining. The location of glial cells was detected by an antiserum against the glial-specific nuclear repo-protein. Lectin-staining surrounded the neuropile of the antennal lobe, axonal projections of olfactory relay neurons, and the mushroom body neuropile. Within the mushroom body neuropile of the bee, DSL-staining was especially intense at the branching sites of the Kenyon cell axons and in the ventral part of the alpha-lobe. The dissection of the various cellular contributions to the lectin-staining in dissociated cell cultures suggested that certain glial cells, but also neuronal somata of the antennal lobe and Kenyon cells of the mushroom bodies express the label. The expression of lectin-staining matures during the pupal development of the bee, whereas in larval stages of the hemimetabolous locust, the staining pattern appears already completed. Since carbohydrate recognition is thought to play an important role in the formation of neuronal networks, the glial derived extracellular material may contribute to the morphogenesis and structural integrity of the olfactory neuropiles.