Locust Medial Neurosecretory Cells in vitro: Morphology, Electrophysiological Properties and Effects of Temperature

The medial neurosecretory cells of the pars intercerebralis in the protocerebrum of larval and adult locusts (Locusta migratoria) were cultured in a chemically defined serum-free culture medium. The morphology of the cells was investigated by light microscopy and the electrophysiological properties were studied using the patch-clamp technique in the whole-cell configuration. The dissociated neurosecretory cells grew new processes under these conditions and were maintained in culture for up to 2 months. The percentage of cells showing outgrowth was significantly higher in third-instar larvae than in instars 4 and 5 and adults. A primary axonal stump promoted a unipolar cell morphology; in other cases, most neurosecretory cells became multipolar. The presence of glial cells in undissociated groups of neurosecretory cells improved outgrowth and the formation of neurite bundles. A considerable number of the recorded cells showed spiking activity in response to depolarization. The influences of temperature on spike frequency, duration and amplitude as well as on membrane potential and ionic currents were investigated. The results suggest that temperature may directly affect the function of neurosecretory cells.