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. 2004 Apr 21;24(16):3974–3984. doi: 10.1523/JNEUROSCI.3720-03.2004

Figure 1.

Figure 1.

Intrinsic osmosensitivity is a unique property of the MnPO neurons. A, Depolarization of a ventral MnPO neuron with current injection triggered a regular spiking activity. Local and transient (1min) application of hypotonic aCSF (270 mOsm/l; 100 mm NaCl) over the vMnPO region hyperpolarized the neuron with a concomitant abolition of the spike discharges (top trace). The same neuron was held below the spike threshold, and local application of hypertonic aCSF (330 mOsm/l; 170 mm NaCl) depolarized the neuron that discharged a prolonged burst of spikes (bottom trace). Details of the spiking activity was illustrated before (*) and after (**) application of the modified aCSF. B, TTX (0.5 μm) was bath applied to block synaptic inputs onto the recorded vMnPO neuron. Under this steady-state synaptic blockage, transient and local application of a hypotonic aCSF hyperpolarized the neuron (top trace). In contrast, local application of a hypertonic aCSF induced a depolarization (bottom trace). C, Local application of hypertonic aCSF did not alter the membrane potential of this vMnPO neuron, which was considered as a non-osmoresponsive neuron. D, Local application of hypotonic aCSF did not change the membrane potential of the neurons located in a region adjacent to the MnPO, the median septum. Note that spike amplitude has been truncated in the traces presented here. These results indicate that detection of the extracellular tonicity involved intrinsic properties of a specific neuronal population of the vMnPO. HP, Holding potential.