Bradley Samual P, Chapman Phillip D, Lizbinski Kristyn M, Daly Kevin C, Dacks Andrew M
Department of Biology, West Virginia University, Morgantown WV, USA.
Front Neural Circuits. 2016 Feb 16;10:5. doi: 10.3389/fncir.2016.00005. eCollection 2016.
Neural circuits projecting information from motor to sensory pathways are common across sensory domains. These circuits typically modify sensory function as a result of motor pattern activation; this is particularly so in cases where the resultant behavior affects the sensory experience or its processing. However, such circuits have not been observed projecting to an olfactory pathway in any species despite well characterized active sampling behaviors that produce reafferent mechanical stimuli, such as sniffing in mammals and wing beating in the moth Manduca sexta. In this study we characterize a circuit that connects a flight sensory-motor center to an olfactory center in Manduca. This circuit consists of a single pair of histamine immunoreactive (HA-ir) neurons that project from the mesothoracic ganglion to innervate a subset of ventral antennal lobe (AL) glomeruli. Furthermore, within the AL we show that the M. sexta histamine B receptor (MsHisClB) is exclusively expressed by a subset of GABAergic and peptidergic LNs, which broadly project to all olfactory glomeruli. Finally, the HA-ir cell pair is present in fifth stage instar larvae; however, the absence of MsHisClB-ir in the larval antennal center indicates that the circuit is incomplete prior to metamorphosis and importantly prior to the expression of flight behavior. Although the functional consequences of this circuit remain unknown, these results provide the first detailed description of a circuit that interconnects an olfactory system with motor centers driving flight behaviors including odor-guided flight.
从运动通路向感觉通路投射信息的神经回路在各个感觉领域都很常见。这些回路通常会因运动模式的激活而改变感觉功能；在由此产生的行为影响感觉体验或其处理过程的情况下尤其如此。然而，尽管存在特征明确的主动采样行为，如哺乳动物的嗅吸和烟草天蛾的振翅，这些行为会产生再传入的机械刺激，但在任何物种中都未观察到这样的回路投射到嗅觉通路。在本研究中，我们描述了烟草天蛾中一条连接飞行感觉运动中心与嗅觉中心的回路。该回路由一对组胺免疫反应性（HA-ir）神经元组成，它们从中胸神经节投射出来，支配腹侧触角叶（AL）的一部分肾小球。此外，在触角叶内，我们发现烟草天蛾组胺B受体（MsHisClB）仅由一部分GABA能和肽能的局部神经元（LN）表达，这些局部神经元广泛投射到所有嗅觉肾小球。最后，HA-ir细胞对存在于五龄幼虫中；然而，幼虫触角中心缺乏MsHisClB-ir表明该回路在变态之前，重要的是在飞行行为表达之前是不完整的。尽管该回路的功能后果尚不清楚，但这些结果首次详细描述了一条将嗅觉系统与驱动飞行行为（包括气味引导飞行）的运动中心相互连接的回路。
