Cellular mechanism for the temperature sensitive spatial orientation in Clione

THE swimming mollusk Clione is normally oriented vertically. As water is warmed, this orientation is lost or reversed. CPB3 interneurons, which transmit signals from the statocyst receptors (SRCs) to the tail motoneurons and play a key role in space orientation, were strongly depolarized upon warming. Normally, intracellular stimulation of the rostro-dorsal SRC (DSRC) excited CPB3b. Upon warming the excitation gradually decreased and in some cases was even replaced by inhibition. The reversal potential for the synaptic potentials (PSP) produced in CPB3b by DSRC stimulation is depolarized relative to the normal membrane potential at lower temperature. Warming causes depolarization of the membrane potential such that the PSP reversal potential is approached and even passed, with attenuant effects on PSP amplitude and polarity. This effect provides a mechanism for the temperature sensitive changes in the orientation of Clione.