Tsuji Takahiro, Tsuji Chiharu, Lozic Maja, Ludwig Mike, Leng Gareth
Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
Department of Immunology, Centre for Neuroendocrinology, University of Pretoria, Pretoria, South Africa.
Physiol Rep. 2019 Nov;7(22):e14284. doi: 10.14814/phy2.14284.
Odorant molecules stimulate olfactory receptor neurons, and axons of these neurons project into the main olfactory bulb where they synapse onto mitral and tufted cells. These project to the primary olfactory cortex including the anterior olfactory nucleus (AON), the piriform cortex, amygdala, and the entorhinal cortex. The properties of mitral cells have been investigated extensively, but how odor information is processed in subsequent brain regions is less well known. In the present study, we recorded the electrical activity of AON neurons in anesthetized rats. Most AON cells fired in bursts of 2-10 spikes separated by very short intervals (<20 ms), in a period linked to the respiratory rhythm. Simultaneous recordings from adjacent neurons revealed that the rhythms of adjacent cells, while locked to the same underlying rhythm, showed marked differences in phase. We studied the responses of AON cells to brief high-frequency stimulation of the lateral olfactory tract, mimicking brief activation of mitral cells by odor. In different cells, such stimuli evoked transient or sustained bursts during stimulation or, more commonly, post-stimulation bursts after inhibition during stimulation. This suggests that, in AON cells, phase shifts occur as a result of post-inhibitory rebound firing, following inhibition by mitral cell input, and we discuss how this supports processing of odor information in the olfactory pathway. Cells were tested for their responsiveness to a social odor (the bedding of a strange male) among other simple and complex odors tested. In total, 11 cells responded strongly and repeatedly to bedding odor, and these responses were diverse, including excitation (transient or sustained), inhibition, and activation after odor presentation, indicating that AON neurons respond not only to the type of complex odor but also to temporal features of odor application.
气味分子刺激嗅觉受体神经元，这些神经元的轴突投射到主嗅球，在那里它们与二尖瓣细胞和簇状细胞形成突触。这些细胞投射到初级嗅觉皮层，包括前嗅核（AON）、梨状皮层、杏仁核和内嗅皮层。二尖瓣细胞的特性已被广泛研究，但气味信息在后续脑区中是如何处理的却鲜为人知。在本研究中，我们记录了麻醉大鼠AON神经元的电活动。大多数AON细胞以2 - 10个尖峰的爆发形式放电，间隔非常短（<20毫秒），这一时期与呼吸节律相关。对相邻神经元的同步记录显示，相邻细胞的节律虽然锁定在相同的潜在节律上，但在相位上存在明显差异。我们研究了AON细胞对外侧嗅束短暂高频刺激的反应，模拟气味对二尖瓣细胞的短暂激活。在不同的细胞中，这种刺激在刺激期间诱发短暂或持续的爆发，或者更常见的是，在刺激期间抑制后出现刺激后爆发。这表明，在AON细胞中，相位变化是由于二尖瓣细胞输入抑制后的抑制后反弹放电导致的，我们讨论了这如何支持嗅觉通路中气味信息的处理。在测试的其他简单和复杂气味中，对细胞对社交气味（陌生雄性的 bedding）的反应性进行了测试。总共11个细胞对 bedding 气味强烈且反复做出反应，这些反应各不相同，可以是兴奋（短暂或持续）、抑制以及气味呈现后的激活，这表明AON神经元不仅对复杂气味的类型有反应，而且对气味施加的时间特征也有反应。
