Membrane properties of rat magnocellular neuroendocrine cells in vivo.

Membrane properties of rat magnocellular neuroendocrine cells (MNCs) were examined during intracellular recordings in vivo. Current-clamp experiments revealed sustained outward rectification positive to -55 mV and transient outward rectification of depolarizing responses elicited from negative holding potentials. Trains of impulses were associated with a progressive increase of spike duration. Such features, which were not observed in neighboring non-neuroendocrine cells, are similar to those of MNCs in slices or explants of rat hypothalamus. In contrast, however, cells recorded in vivo were characterized by intense synaptic inhibition and a lower specific impedance than commonly observed from MNCs impaled in vitro.