| 'Transduction' in receptor cells is the conversion of one form of stimulus energy into another. The term implicitly refers to open loop systems. The open loop concept is incompatible with the combined electrosensitivity and chemosensitivity of electroreceptor cells in freshwater fish, however. A new working hypothesis was therefore formulated: if a closed loop concept is adopted, which describes the homeostatic regulation of the receptor cell interior, any electrochemical disturbance of the cellular homeostasis can play the role of a stimulus. In this view, the error signal controlling the feedback is the effective stimulus. Support for the validity of such a model comes from the existence of 'dark currents' in photoreceptor cells, and 'K+-currents' in taste cells in vertebrates. Experiments are designed to characterise step by step what subcellular systems are crucial and in what way. Since cellular homeostasis is a general process in cell survival, that of electroreceptors will be compared to homeostasis in other sensory cells in the integument of other (preferably aquatic) organisms. |
