- 作者: J.C. Yen Julie Y.H. Chan Samuel H.H. Chan
- 作者服務機構: Institute of Pharmacology, National Yang-Ming University, Taipei, Taiwan, Department of Medical Education and research, veterans general hospital-Kaohsiung, Center for Neuroscience and Department of biological Science, National Sun Yat-Sen University, Kaohsiung, aiwan, ROC
- 中文摘要: --
- 英文摘要: We delineated the role of Ca -activated K channels inthe phenomenon of spike frequency adaptation (SFA)exhibited by neurons in the caudal region of nucleustractus solitarius (cNTS) using intracellular recordingcoupled with the current-clamp technique in rat brainslices. Intracellular injection of a constant depolarizingcurrent evoked a train of action potentials whose dis-charge frequency declined rapidly to a lower steady-state level of irregular discharges. This manifested phe-nomenon of SFA was found to be related to extracellularCa . Low Ca (0.25 mM) or Cd (0.5 mM) in the perfus-ing medium resulted in a significant increase in the adap-tation time constant (τ ) and an appreciable reductionin the percentage adaptation of spike frequency (F ). Inaddition, the evoked discharges were converted from anirregular to a regular pattern, accompanied by a pro-found increase in mean firing rate. Intriguingly, similaralterations in τ , F , discharge pattern and dis-charge rate were elicited by apamin (1μM), a selectiveblocker for small-conductance Ca -activated K (SK)channels. On the other hand, charybdotoxin(0.1μM), aselective blocker for large-conductance Cat+-activated K channels, was ineffective. Our results suggest that SKchannels of cNTS neurons may subserve the generationof both SFA and irregular discharge patterns displayedby action potentials evoked with a prolonged depolariz-ing current.
- 中文關鍵字: --
- 英文關鍵字: Spike Frequency adaptation. Small-conductance K Channel. Nucleus tractus solitarii. Apamin. Charybdotoxin