Zornik Erik, Kelley Darcy B
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
J Neurosci. 2008 Jan 16;28(3):612-21. doi: 10.1523/JNEUROSCI.4754-07.2008.
The aquatic frog Xenopus laevis uses a complex vocal repertoire during mating and male-male interactions. Calls are produced without breathing, allowing the frogs to vocalize for long periods underwater. The Xenopus vocal organ, the larynx, is innervated by neurons in cranial motor nucleus (n.) IX-X, which contains both vocal (laryngeal) and respiratory (glottal) motor neurons. The primary descending input to n.IX-X comes from the pretrigeminal nucleus of the dorsal tegmental area of the medulla (DTAM), located in the rostral hindbrain. We wanted to characterize premotor inputs to respiratory and vocal motor neurons and to determine what mechanisms might be involved in regulating two temporally distinct rhythmic behaviors: breathing and calling. Using isolated brain and larynx preparations, we recorded extracellular activity from the laryngeal nerve and muscles and intracellular activity in laryngeal and glottal motor neurons. Spontaneous nerve activities mimicking respiratory and vocal patterns were observed. DTAM projection neurons (DTAM(IX-X) neurons) provide direct input to glottal and laryngeal motor neurons. Electrical stimulation produced short-latency coordinated activity in the laryngeal nerve. DTAM(IX-X) neurons provide excitatory monosynaptic inputs to laryngeal motor neurons and mixed excitatory and inhibitory inputs to glottal motor neurons. DTAM stimulation also produced a delayed burst of glottal motor neuron activity. Together, our data suggest that neurons in DTAM produce vocal motor output by directly activating laryngeal motor neurons and that DTAM may coordinate vocal and respiratory motor activity.
水生蛙非洲爪蟾在交配和雄性间互动时会使用复杂的发声 repertoire。其叫声是在不呼吸的情况下产生的，这使得青蛙能够在水下长时间发声。非洲爪蟾的发声器官——喉部，由位于颅神经运动核（n.）IX - X中的神经元支配，该核包含发声（喉部）和呼吸（声门）运动神经元。对n.IX - X的主要下行输入来自延髓背侧被盖区的三叉前核（DTAM），位于后脑前部。我们想要描述呼吸和发声运动神经元的运动前输入，并确定可能参与调节两种在时间上不同的节律性行为的机制：呼吸和鸣叫。使用离体脑和喉部标本，我们记录了喉神经和肌肉的细胞外活动以及喉部和声门运动神经元的细胞内活动。观察到了模仿呼吸和发声模式的自发神经活动。DTAM投射神经元（DTAM(IX - X)神经元）直接向声门和喉部运动神经元提供输入。电刺激在喉神经中产生短潜伏期的协调活动。DTAM(IX - X)神经元向喉部运动神经元提供兴奋性单突触输入，向声门运动神经元提供混合的兴奋性和抑制性输入。DTAM刺激还产生了声门运动神经元活动的延迟爆发。总之，我们的数据表明DTAM中的神经元通过直接激活喉部运动神经元产生发声运动输出，并且DTAM可能协调发声和呼吸运动活动。
