Morphophysiologic properties of islet cells in substantia gelatinosa of the rat spinal cord

Substantia gelatinosa (SG) neurons of the spinal cord are highly heterogeneous in their morphophysiologic properties and could be categorized on several subtypes. Here the properties of islet cells in rat SG (∼11%) are described with the use of confocal microscopy and patch-clamp recording. The cells had significantly longer and thicker dendritic trees among all other neurons. Only these cells expressed slow inward current activated by hyperpolarization, which could be blocked by Cs+ but not Ba2+, presumably representing H-current (Ih). Possibly due to Ih, islet cells had peculiar membrane and firing responses. Of note the membrane potential showed a sag in response to hyperpolarization while depolarization triggered action potentials (APs) in a tonic-like pattern. APs, however, occurred with larger maximal frequencies and in response to broader stimulation intensities than in other tonically firing neurons. Neuronal variability in SG and possible functional roles of islet cells are discussed.