Properties of Action Potential Waveform-Evoked L-type Calcium Currents in Pituitary GH3 Cells
The purpose of this study was to examine the time course and kinetics of L-type Ca2+ current (ICa,L) from pituitary GH3 cells in response to various action potential (AP) waveforms using the whole-cell configuration of the patch-clamp technique. The major findings in this study are:
1. ICa,L evoked during the AP waveform exhibited an early and a late component. The early component of ICa,L occurred on the rising phase of the AP, whereas the late component coincided with the falling phase.
2. A prolongation of the falling phase of APs led to an increase in Ca2+ charge carried by ICa,L, although the amplitude of the late ICa,L was reduced.
3. When the peak voltage of AP waveforms was prolonged without changing the rising and falling phases, the amplitude of the late components was significantly increased.
4. ICa,L was also found to inactivate during a train of AP waveforms. When Ba2+ ions were used as the charge carriers, current inactivation during a train of APs was decreased.
5. The amplitude of ICa,L evoked by the AP templates with irregular bursting pattern was inactivated.
6. When spontaneous APs with the depolarizing potentials were replayed to GH3 cells, Ca2+ entry was not only spread over the entire AP, but also occurred during the interspike voltage trajectory.
7. When cells were exposed to thyrotropin releasing hormone (TRH; 10
Advisor:Hung-Tu Huang; Sheng-Nan Wu; Chung-Ren Jan
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:action potential gh3 patch clamp trh
Date of Publication:06/20/2002