title: Long-lasting enhancement in the intrinsic excitability of deep dorsal horn neurons.
abstract: Intrinsic excitability (IE) can be defined as an output of action potentials from a given input signal. Changes to the IE of a neuron are an important aspect of the cellular plasticity that underlies learning and memory process. In this study, long-term plastic change in IE of deep dorsal horn neurons (DHNs) was investigated. Associative spike pairing stimulation (PS) induced a long-lasting increase in IE. Buffering intracellular calcium with BAPTA (10mM) prevented the induction of a long-lasting increase in IE. PS failed to induce a long-lasting increase in IE in the presence of either D-APV (50 microM) or cadmium chloride (100 microM). Apamin (100 nM) partially blocked the induction of a long-lasting increase in IE. This intrinsic plasticity requires a rise in postsynaptic Ca(2+) and NMDA receptor activation during the induction period, and this process might be mediated by the down-regulation of small-conductance calcium-dependent potassium (SK) channels. In deep DHNs, PS induced excitatory postsynaptic potential (EPSP)-spike (E-S) potentiation, which increases the firing probability and the number of spikes, by consistent dorsal rootlet stimulation. Under bath application of bicuculline (10 microM) and strychnine (1 microM), PS induced E-S potentiation and long-lasting increases in IE. These results suggest that an increase in IE might underlie E-S potentiation, while a reduction in inhibitory transmission does not contribute to E-S potentiation and long-lasting increases in IE. We conclude that PS enhances the IE of deep DHNs, which may play an important role in spinal processing of nociceptive information.
authors.affiliation: Department of Physiology, Konyang University College of Medicine, Daejeon, Republic of Korea Department of Physiology, Inha University College of Medicine, Incheon, Republic of Korea Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Dong Kwan
authors.initials: DK
authors.lastname: Kim
authors.forename: Jiyeon
authors.initials: J
authors.lastname: Kwak
authors.forename: Sang Jeong
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jun
authors.initials: J
authors.lastname: Kim
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D017774:Long-Term Potentiation / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D020671:Posterior Horn Cells / Q000502:physiology*; D051381:Rats