Ionic currents underlying rhythmic bursting of ventral mossy cells in the developing mouse dentate gyrus.
The electrophysiological properties of mossy cells were examined in developing mouse hippocampal slices using whole-cell patch-clamp techniques, with particular reference to the dorsoventral difference. Dorsal mossy cells exhibited a higher spontaneous excitatory postsynaptic potential (EPSP) frequency and larger maximal EPSP amplitude than ventral mossy cells. On the other hand, the blockade of synaptic inputs with glutamatergic and GABAergic antagonists disclosed a remarkable dorsoventral difference in the intrinsic activity: none (0/27) of the dorsal mossy cells showed intrinsic bursting, whereas the majority (35/47) of the ventral mossy cells exhibited intrinsic rhythmic bursting. To characterize the ionic currents underlying the rhythmic bursting of mossy cells, we used somatic voltage-clamp recordings in the subthreshold voltage range. Ventral bursting cells possessed both hyperpolarization-activated current (Ih) and persistent sodium current (INaP), whereas dorsal and ventral nonbursting cells possessed Ih but no INaP. Blockade of Ih with cesium did not affect the intrinsic bursting of ventral mossy cells. In contrast, the blockade of INaP with tetrodotoxin or phenytoin established a stable subthreshold membrane potential in ventral bursting cells. The current-voltage curve of ventral bursting cells showed a region of tetrodotoxin-sensitive negative slope conductance between -55 mV and a spike threshold ( approximately -45 mV). On the other hand, no subthreshold calcium conductances played a significant role in the intrinsic bursting of ventral mossy cells. These observations demonstrate the heterogeneous electrophysiological properties of hilar mossy cells, and suggest that the subthreshold INaP plays a major role in the intrinsic rhythmic bursting of ventral mossy cells.
Jinno
Shozo
S
Kyushu University, Department of Anatomy & Neurobiology, Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. sjnno@med.kyushu-u.ac.jp
Ishizuka
Satoru
S
Kosaka
Toshio
T
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D001640:Bicuculline / Q000031:analogs & derivatives* / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D064032:Calbindin 2; D002586:Cesium / Q000494:pharmacology; D018891:Dentate Gyrus / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D004338:Drug Combinations; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018756:GABA Antagonists / Q000494:pharmacology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal / Q000295:instrumentation; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D010672:Phenytoin / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
D000779:Anesthetics, Local; D000927:Anticonvulsants; D064032:Calbindin 2; D004338:Drug Combinations; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D007473:Ion Channels; D007527:Isoenzymes; D011810:Quinoxalines; D064030:S100 Calcium Binding Protein G; D002104:Cadmium; D002586:Cesium; C017069:bicuculline methiodide; D013779:Tetrodotoxin; D010672:Phenytoin; C056723:FG 9041; D015763:2-Amino-5-phosphonovalerate; D009532:Nickel; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; D001640:Bicuculline