Functional Role of A-Type Potassium Channels in A7 Catecholamine Cell Group in Rats

• Main Authors: Yu-Wei Wu, 吳玉威
• Other Authors: Ming-Yuan Min
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/42512552656408337765

碩士 === 國立臺灣大學 === 動物學研究研究所 === 95 === The pontine noradrenergic (NAergic) neurons located in A7 area are believed to play an important role in modulating nociception. This study provides the first functional analysis of the biophysical and pharmacological properties of A-type current (IA) in A7 NAergic neurons. IA in A7 NAergic neurons was activated at about -70 mV, with midpoint activation potential of -27.97 ± 1.71 mV. The midpoint inactivation potential was at about -72.31 ± 2.27 mV, and the recovery from inactivation was very quickly with a time constant of 21.87 ± 2.80 ms at Vm = -100 mV. The IA was sensitive to heteroprodotoxin2 (HpTx2), a Kv4 selective blocker, but not affected by BDS-I, a Kv3.4 selective blocker. These biophysical and pharmacological results demonstrated that A-type current in A7 NAergic neurons is mediated mainly by Kv4. By immunostaing, we found that Kv4.3 proteins were robustly expressed on the soma and dendrites. This result indicated that the A-type in A7 NAergic neurons may mediated by somatodendritic Kv4.3. This A-type current acted not only at subthreshold level to control the initiation of action potential and firing frequency, but was also activated at suprathreshold to shape the action potentials. Furthermore, it could be activated by membrane depolarization during excitatory synaptic transmission and might contribute to the synaptic signal propagation and integration in A7 NAergic neurons. These findings may help us understand more about the regulation of pain transmission.