Action of an Osmoreceptor

Actin filaments in brain osmoreceptors detect changes in solute concentration in the interstitial fluid when the cell membrane expands or contracts. Changes in cell volume cause changes in the membrane potential, which serve as the signal for osmometric thirst. (a) When a hypotonic solution was added to the culture medium of an isolated osmoreceptor, the cell volume increased and the membrane potential decreased. When suction was then applied through the micropipette, the cell volume decreased and the membrane potential increased.  (Adapted from Zhang, Z., Kindrat, A. N., Sharif-Naeini, R., and Bourque, C. W. Journal of Neuroscience, 2007, 27, 4008–4013.)