Taurine-, aspartate- and glutamate-like immunoreactivity identifies chemically distinct subdivisions of Kenyon cells in the cockroach mushroom body

The lobes of the mushroom bodies of the cockroach Periplaneta americana con sist of longitudinal modules called laminae. These comprise repeating arran gements of Kenyon cell axons, which like their dendrites and perikarya. hav e an affinity to one of three antisera: to taurine, aspartate, or glutamate . Taurine-immunopositive laminae alternate with immunonegative ones. Aspart ate-immunopositive Kenyon cell axons are distributed across the lobes. Howe ver, smaller leaf-like ensembles of axons that reveal particularly high aff inities to anti-aspartate are embedded within taurine-positive laminae and occur in the immunonegative laminae between them. Together, these arrangeme nts reveal a complex architecture of repeating subunits whose different lev els of immunoreactivity correspond to broader immunoreactive layers identif ied by sera against the neuromodulator FMRFamide. Throughout development an d in the adult, the most posterior lamina is glutamate immunopositive. Its axons arise from the most recently born Kenyon cells that in the adult reta in their juvenile character, sending a dense system of collaterals to the f ront of the lobes. Glutamate-positive processes intersect aspartate- and ta urine-immunopositive laminae and are disposed such that they might play imp ortant roles in synaptogenesis or synapse modification. Glutamate immunorea ctivity is not seen in older, mature axons, indicating that Kenyon cells sh ow plasticity of neurotransmitter phenotype during development. Aspartate m ay be a universal transmitter substance throughout the lobes. High levels o f taurine immunoreactivity occur in broad laminae containing the high conce ntrations of synaptic vesicles. (C) 2001 Wiley-Liss, Inc.