[Morphophysiologic properties of delayed firing neurons in substantia gelatinosa of the rat spinal cord.
Substantia gelatinosa (SG) neurons of the spinal cord are highly heterogeneous in their morphologic and physiologic properties. Based on characteristic firing response evoked by sustained depolarization, neurons can be categorized on three main types: tonic, adapting and delayed firing (DFNs). Here, properties of DFNs in spinal cord slices from 3-5 weeks-old rats were studied with the use of patch-clamp recording and confocal microscopy. Distinctive features of DFNs were increased rheobase (95.7 +/- 11.2 pA) and depolarized threshold to evoke action potential (-37.8 +/- 0.7 mV) than in neurons of other types. In voltage-clamp mode all DFNs expressed high amplitude outward A-type potassium current (K(A)), which started activation at approximately -70 mV, before Na+ current. Structurally, the majority of DFNs had vertically oriented dendritic tree, while their axons were not restricted to SG and projected predominantly to lamina I. Possible physiological functions of DFNs are discussed.
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O.O. Bogomoletz Institute of Physiology National Academy of Sciences of Ukraine, Kvyiv. _igorm@biph.kiev.ua
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology* / Q000648:ultrastructure; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology / Q000648:ultrastructure; D013376:Substantia Gelatinosa / Q000502:physiology* / Q000648:ultrastructure*; D013997:Time Factors