[β2-nicotinic acetylcholine receptor promotes development of GABAA receptors in mouse hippocampal CA1 and CA3 pyramidal neurons]

Abstract

Objective: To explore the role of β2-nicotinic acetylcholine receptor (β2-nAChR) in the development of γ- aminobutyric acid A type receptors (GABA_A-Rs) in hippocampal CA1 and CA3 pyramidal neurons of mice.

Methods: The hippocampal CA1 and CA3 pyramidal neurons were acutely isolated from β2-nAChR gene knockout (β2-KO group) mice. GABA currents in CA1 and CA3 pyramidal neurons were induced with the selective GABA_A-R agonist muscimol and recorded using perforated patch-clamp recording technique. The GABA currents of CA1 and CA3 pyramidal neurons were tested for their equilibrium potentials (E_Muss) and kinetic parameters and were compared with the measurements in wild-type mice (WT group).

Results: The mean E_Mus of CA1 neurons (n=7) of β2-KO mice (n=4) was -31.7±3.5 mV, showing an obvious depolarizing shift compared with the WT mice (P < 0.05); the mean E_Mus of CA3 neurons (n=4) was -16.1±4.6 mV, also showing a depolarizing shift (P < 0.01). The difference in the E_Muss between CA3 and CA1 neurons in β2-KO mice, but not in WT mice, was significant (P < 0.05). The GABA_A-R desensitization was significantly slowed down in both CA1 and CA3 neurons of β2-KO mice, with decay time of 2.2±0.2 s and 3.2±0.1 s, respectively, significantly longer than those in WT mice (1.6±0.1 s and 2.3±0.1 s, respectively; P < 0.05).

Conclusions: β2-containing nAChRs may promote the functional maturation of GABA_A-R in CA1 and CA3 pyramidal cells in mouse hippocampus.

Keywords: equilibrium potential of muscimol-induced currents; gene knockout; hippocampus; kinetic indexes; β2-nicotinic acetylcholine receptors; γ-aminobutyric acid A type receptors.

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野生型和β2-KO小鼠海马CA1神经元上GABA_A-R平衡电位的比较 Comparisons on the equilibrium potential (E_Mus) mediated by GABA_A-Rs in the hippocampal CA1 neurons between WT and β2-KO mice. A, C: Typical currents induced by muscimol, the GABA_A-R selective agonist, were recorded in a WT CA1(A) and a β2-KO CA1 (C) neuron respectively at the different holding potentials (V_Hs) indicated on the left of each current curve; B, D: Amplitude of peak current and matched V_H were plotted to yield the E_Mus from a linear fit of the I-V curve for each cell corresponding to A and C. In D, the regression line was extra plotted to positive direction.

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野生型和β2-KO小鼠海马CA1和CA3神经元上GABA_A-R平衡电位的比较 Bar chart summarizing the difference of the equilibrium potentials (E_Muss) mediated by GABA_A-Rs in the hippocampus CA1 and CA3 neurons obtained from the WT and β2-KO mice. Cell numbers were marked in the corresponding brackets above each bar. ^*P < 0.05, ^**P < 0.01.

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野生型和β2-KO小鼠CA3神经元上GABA_A-R平衡电位的差异 Differences in the equilibrium potential (E_Mus) mediated by GABA_A-Rs in the hippocampus CA3 neurons obtained from the WT and β2- KO mice. A, C: Representative currents induced by muscimol were recorded at the indicated V_Hs in a WT (A) and a β2-KO (C) neuron; B, D: Peak amplitude of the GABA_A-R-mediated currents as a function of voltage in a WT (B) and a β2-KO (D) neuron as in A and C. The regression line was extra plotted to positive direction in D.

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野生型和β2-KO小鼠CA1神经元上GABA_A-R介导电流的动力学比较 Comparisons of kinetics of GABA_A-R-mediated currents in CA1 neurons of WT and β2-KO mice. A: Representative currents induced by muscimol were recorded in the CA1 neurons respective from WT (gray) and β2-KO (black) mice; B: Quantification of rise time (left) and decay time (right) of the GABA_A-R-mediated currents as in A. Cell numbers are marked inside the bars. ^*P < 0.05.

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野生型和β2-KO小鼠CA3神经元上GABA_A-R介导电流的动力学差异 Differences in kinetics of GABA_A-R-mediated currents in CA3 neurons between WT and β2- KO mice. A: Typical currents induced by muscimol were recorded in the CA3 neurons respective from WT (gray) and β2-KO (black) mice; B: Quantification of rise time (left) and decay time (right) of the GABA_A-R-mediated currents as in A. Cell numbers are marked inside the bars. ^**P < 0.01.