An analysis of the effects of stimulus transport and membrane charge on the salt, acid and water-response of mammals

Abstract

We present an analysis of stimulus transport in mammalian taste reception emphasizing the coupling between hydrodynamic and diffusive mass transfer. We show that flow-rate dependence in the phasic portions of the gustatory response can be explained by a flow-velocity dependent diffusionboundary layer in series with a flow-indifferent path length. Using data from the literature we show that the concentration dependence of the neural latency to NaCl stimulation in the rat and the threshold concentration can be accounted for by the time course of stimulus arrival and need not imply a uniquely slow sensory transduction process. We develop a generalized response function which describes aspects of the early phasic neural response and shows that early events are governed solely by the local concentration of stimulus. This too is confirmed by data in the literature. The surface pressure is characterized as an example of a nonmonotonic response function which can account for the general properties of the salt, acid and water response. In vitro studies on phopholipid monolayers conform to the theory. It is suggested that surface activity may be critical in transduction and that surface active agents can have profound effects on taste reception.