Evaluation of Ca2+ permeability of nicotinic acetylcholine receptors in hypothalamic histaminergic neurons.
Evaluation of Ca2+ permeability of nicotinic acetylcholine receptors in hypothalamic histaminergic neurons.
复制标题
DOI：
10.1093/abbs/gmp101
复制
发表时间：
2010
影响因子：
3.7
通讯作者：
Victor V Uteshev
中科院分区：
文献类型：
--
作者：
Victor V Uteshev
下丘脑组胺能结节乳头(TM)神经元表达烟碱型乙酰胆碱受体(NAChRs)，其动力学和药理学特性类似于高Ca(2+)通透性α7 nAChRs。然而，TM nAChR通道的Ca(2+)通透性尚未被测定。为了直接评价TM nAChRs的钙通透性，用未培养的急性分离的TM神经元和含低(2 MM)和高(20 MM)Ca(2+)的外液进行膜片钳记录。根据电流-电压关系确定了反转电位的移动，并在Goldman-Hodgkin-Katz恒定磁场近似下估计了渗透率比P(Ca)/P(Na)。在-60 mV下，TM nAChRs具有高的Ca(2+)渗透性，渗透率比P(Ca)/P(Na)(NAChR)约为5.9，分数Ca(2+)电流P(F)(NAChR)约为10.1%。作为所用方法和分析的阳性对照，利用未培养的急性分离的海马锥体神经元，测定了NMDA受体的通透性比P(Ca)/P(Na)(NMDAR)约为8.3，在-60 mV时的钙电流分数P(F)(NMDAR)约为13.6%，结果与先前报道的值相似。因此，这些结果表明，天然TM nAChRs对Ca(2+)具有高度的通透性，但对Ca(2+)的通透性大约是天然海马锥体NMDA受体的1.4倍。
Hypothalamic histaminergic tuberomammillary (TM) neurons express nicotinic acetylcholine receptors (nAChRs) with kinetic and pharmacological properties resembling those of highly Ca(2+) permeable alpha7 nAChRs. However, the Ca(2+) permeability of TM nAChR channels has not been determined. To directly evaluate the Ca(2+) permeability of TM nAChRs, patch-clamp recordings were conducted using non-cultured acutely dissociated TM neurons and external solutions containing low (2 mM) and high (20 mM) concentrations of Ca(2+). A shift in the reversal potentials was determined from the current-voltage relationships and the permeability ratio, P(Ca)/P(Na), was estimated within the Goldman-Hodgkin-Katz constant field approximation. TM nAChRs were found to be highly Ca(2+) permeable with the permeability ratio, P(Ca)/P(Na)(nAChR) being approximately 5.9 and the fractional Ca(2+) current, P(f)(nAChR) being approximately 10.1% at -60 mV. As a positive control for the applied methods and analysis, the permeability ratio, P(Ca)/P(Na)(NMDAR) being approximately 8.3 and the fractional Ca(2+) current, P(f)(NMDAR) being approximately 13.6% at -60 mV for NMDA receptors were determined using non-cultured acutely dissociated hippocampal pyramidal neurons and found similar to previously reported values. Therefore, these results demonstrate that native TM nAChRs are highly Ca(2+) permeable, but approximately 1.4 fold less permeable to Ca(2+) than native hippocampal pyramidal NMDA receptors.