Azevedo Anthony W, Wilson Rachel I
Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Neuron. 2017 Oct 11;96(2):446-460.e9. doi: 10.1016/j.neuron.2017.09.004. Epub 2017 Sep 21.
To better understand biophysical mechanisms of mechanosensory processing, we investigated two cell types in the Drosophila brain (A2 and B1 cells) that are postsynaptic to antennal vibration receptors. A2 cells receive excitatory synaptic currents in response to both directions of movement: thus, twice per vibration cycle. The membrane acts as a low-pass filter, so that voltage and spiking mainly track the vibration envelope rather than individual cycles. By contrast, B1 cells are excited by only forward or backward movement, meaning they are sensitive to vibration phase. They receive oscillatory synaptic currents at the stimulus frequency, and they bandpass filter these inputs to favor specific frequencies. Different cells prefer different frequencies, due to differences in their voltage-gated conductances. Both Na and K conductances suppress low-frequency synaptic inputs, so cells with larger voltage-gated conductances prefer higher frequencies. These results illustrate how membrane properties and voltage-gated conductances can extract distinct stimulus features into parallel channels.
为了更好地理解机械感觉处理的生物物理机制，我们研究了果蝇大脑中的两种细胞类型（A2和B1细胞），它们是触角振动感受器的突触后细胞。A2细胞在两个运动方向上都会接收兴奋性突触电流：因此，每个振动周期会接收两次。细胞膜起到低通滤波器的作用，因此电压和尖峰主要跟踪振动包络，而不是单个周期。相比之下，B1细胞仅在前向或后向运动时被激发，这意味着它们对振动相位敏感。它们以刺激频率接收振荡性突触电流，并对这些输入进行带通滤波以偏好特定频率。由于电压门控电导的差异，不同的细胞偏好不同的频率。钠电导和钾电导都会抑制低频突触输入，因此具有较大电压门控电导的细胞偏好更高的频率。这些结果说明了膜特性和电压门控电导如何将不同的刺激特征提取到并行通道中。
