Tympanal receptor cells of Schistocerca gregaria: Correlation of soma positions and dendrite attachment sites, central projections and physiologies

By using neurobiotin as a marker in intracellular recordings, we were able to directly correlate soma positions and dendrite attachment sites as well as axonal morphologies and physiologies of single auditory receptor cells o f Schistocerca gregaria. We could clearly discriminate three groups of rece ptor cells, differing in their orientation within the Muller's organ, their central arborizations and their physiology: Group I comprises 20 receptor cells with their dendrites attached to the "f olded body." Their characteristic frequencies (CFs) lie at 400-700 Hz or at 1.5-2 kHz. Group II consists of 12-14 high frequency receptor cells (CFs 1 2-25 kHz) whose dendrites are attached to the "pyriform vesicle." Group III receptor cells dendrites are attached to either the "elevated process" (EP ) or to the "styliform body'' (SB); their CFs lie at 3-4 kHz. There were no differences in physiology and central arborizations between those receptor cells of Group III whose dendrites are attached to the SE and those whose dendrites are attached to the EP. Our method renders it possible to combine previous classifications based on either exclusively morphological (a-, b-, c-, d-cells) or physiological (t ype 1-type 4 cells) findings. In contrast to the hitherto hypothetical indi rect correlations, we correlate c-cells and type 1 cells (= group I; see ab ove) and d-cells to type 4 cells (= group II). Furthermore, we demonstrate that a subdivision of a-cells and b-cells is not reflected in a subdivision of type 2 and type 3 cells. The latter have to be combined into one group (= group III). (C) 1999 Wiley-Liss, Inc.