title: Chronic NGF treatment induces somatic hyperexcitability in cultured dorsal root ganglion neurons of the rat.
abstract: Adult rat dorsal root ganglion (DRG) neurons cultured in the presence of 100-ng/mL NGF were reported to show spontaneous action potentials in the cell-attached recording. In this study, underlying mechanisms were examined in the whole-cell and outside-out voltage clamp recording. In 75% neurons with on-cell firing, transient inward current spikes were repetitively recorded in the voltage clamp mode at -50 mV in the whole-cell configuration (named "Isp"). Isp with stable amplitudes occurred in an all-or-none fashion, and was abolished by TTX (< 100 nM), lidocaine (< 1 mM) and a reduction of extracellular Na(+) (154 to 100 mM) in an all-or-none fashion, suggesting that Isp reflects spontaneous dicharges occurring at the loosely voltage-clamped regions. Isp was also observed in the excised outside-out patches and the kinetics and the sensitivity to TTX and lidocaine resembled those in the whole-cell. Spontaneous action potentials were also recorded in the current clamp mode. Small subthreshold spikes often preceded the action potentials. When the localized discharge affected a whole-somatic membrane potential to overcome a threshold, the action potential generated. These results indicate that the triggering sources of the action potential exist in the somatic membrane itself in NGF-treated DRG neurons.
authors.affiliation: Laboratory of Veterinary Physiology, Faculty of Agriculture, Tottori University, Tottori, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Kayano
authors.forename: Naoki
authors.initials: N
authors.lastname: Kitamura
authors.forename: Taiki
authors.initials: T
authors.lastname: Moriya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kuwahara
authors.forename: You
authors.initials: Y
authors.lastname: Komagiri
authors.forename: Emil C
authors.initials: EC
authors.lastname: Toescu
authors.forename: Izumi
authors.initials: I
authors.lastname: Shibuya
mesh_terms: D000200:Action Potentials; D000818:Animals; D002414:Cations, Monovalent; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D061251:Primary Cell Culture; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D002414:Cations, Monovalent; D013779:Tetrodotoxin; D020932:Nerve Growth Factor; D008012:Lidocaine; D012964:Sodium