Ionic mechanism of mechano-perception in characeae

Characean internodal cells generate receptor potential in response to mechanical stimuli. We studied responses of internodal cells to a long-lasting stimulus and the results were as follows. (i) The cell generated receptor potential at the moment of both compression and decompression. (ii) The receptor potential (Delta E-m) was significantly larger at the moment of decompression than at compression. (iii) The longer the duration of the stimulus, the larger was the magnitude of Delta E-m at the moment of decompression. (iv) Aequorin studies revealed that the increase in [Ca2+](c) (Delta[Ca2+](c)) took place at the moment of both compression and decompression. (v) The amplitude of Delta[Ca2+](c) was larger at the moment of decompression than at compression, as was the case for Delta E (m). It was suggested that the amplitude of the receptor potential had a tight correlation with the degree of membrane deformation. We discussed the ionic mechanism of mechano-perception under a long-lasting stimulus in relation to mechanosensitive activation of Ca2+ channels at the plasma membrane.