Gdovin M J, Torgerson C S, Remmers J E
Division of Life Sciences, University of Texas at San Antonio 78249, USA.
Comp Biochem Physiol A Mol Integr Physiol. 1999 Nov;124(3):275-86. doi: 10.1016/s1095-6433(99)00116-6.
Spontaneous high-frequency, low-amplitude and low-frequency, high-amplitude efferent bursting patterns of cranial and spinal motor nerve activity in the in vitro brainstem preparation of the bullfrog tadpole Rana catesbeiana have been characterized as fictive gill and lung ventilation, respectively (Gdovin MJ, Torgerson CS, Remmers JE). Characterization of gill and lung ventilatory activity in cranial nerves in the spontaneously breathing tadpole Rana catesbeiana, FASEB J 1996;10(3):A642; Gdovin MJ, Torgerson CS, Remmers JE. Neurorespiratory pattern of gill and lung ventilation in the decerebrate spontaneously breathing tadpole, Respir Physiol 1998;113:135 146; Pack AI, Galante RJ, Walker RE, Kubin LK, Fishman AP. Comparative approach to neural control of respiration, In: Speck DF, Dekin MS, Revelette WR, Frazier DT, editors. Respiratory Control Central and Peripheral Mechanisms. Lexington: University of Kentucky Press, 1993:52-57). In addition, the ontogenetic dependence of central respiratory chemoreceptor stimulation on fictive gill and lung ventilation has been previously described (Torgerson CS, Gdovin MJ, Remmers JE. Fictive gill and lung ventilation in the pre- and post-metamorphic tadpole brainstem, J Neurophysiol 1998, in press). To investigate the neural substrates responsible for central respiratory rhythm generation of gill and lung ventilation in the developing tadpole, we recorded efferent activities of cranial nerve (CN) V, VII, and X and spinal nerve (SN) II during changes in superfusate PCO2 before and after multiple transection of the in vitro brainstem. The brainstem was transected between CN VIII and IX and the response to changes in PCO2 was recorded. A second transection was then made between the caudal margin of CN X and rostral to SN II. Preliminary data reveal that robust gill ventilation was recorded consistently only if the segment of brainstem included CN X, whereas the loci capable of eliciting fictive lung bursting patterns appeared to differ depending on developmental stage. These data demonstrate that the neural substrate required for fictive gill and lung ventilation exists in anatomically separate regions such that the gill central pattern generator (CPG) is located in the caudal medulla at the level of CN X throughout development, whereas the location of the lung CPG is located more rostrally at the level of CN VII in the post-metamorphic larva. Both in vivo and in vitro studies revealed two distinct neural bursting patterns associated with gill and lung ventilation. Sequential activation of CN V, VII, X were observed during gill ventilation of in vivo and fictive gill ventilation in vitro, whereas these nerve activities, along with SN II displayed more synchronous bursting patterns of activation during lung ventilation and fictive lung breaths.
在牛蛙蝌蚪（牛蛙）的离体脑干标本中，颅神经和脊髓运动神经活动的自发高频、低振幅以及低频、高振幅传出爆发模式，分别被表征为虚构的鳃呼吸和肺通气（Gdovin MJ、Torgerson CS、Remmers JE）。对自发呼吸的牛蛙蝌蚪颅神经中鳃和肺通气活动的表征（《美国实验生物学会联合会杂志》1996年；10(3):A642；Gdovin MJ、Torgerson CS、Remmers JE）；去大脑自发呼吸蝌蚪中鳃和肺通气的神经呼吸模式（《呼吸生理学》1998年；113:135 - 146；Pack AI、Galante RJ、Walker RE、Kubin LK、Fishman AP）。呼吸控制的中枢和外周机制的比较方法，载于Speck DF、Dekin MS、Revelette WR、Frazier DT编著的《呼吸控制：中枢和外周机制》。列克星敦：肯塔基大学出版社，1993年：52 - 57）。此外，先前已经描述了中枢呼吸化学感受器刺激对虚构鳃和肺通气的个体发育依赖性（Torgerson CS、Gdovin MJ、Remmers JE。变态前和变态后蝌蚪脑干中的虚构鳃和肺通气，《神经生理学杂志》1998年，即将发表）。为了研究发育中蝌蚪鳃和肺通气的中枢呼吸节律产生的神经基础，我们在体外脑干多次横断前后，记录了在灌流液PCO2变化期间颅神经（CN）V、VII和X以及脊髓神经（SN）II的传出活动。在CN VIII和IX之间横断脑干，并记录对PCO2变化的反应。然后在CN X的尾缘和SN II的头侧之间进行第二次横断。初步数据显示，只有当脑干节段包括CN X时，才能持续记录到强烈的鳃通气，而能够引发虚构肺爆发模式的位点似乎因发育阶段而异。这些数据表明，虚构鳃和肺通气所需的神经基础存在于解剖学上不同的区域，使得鳃中枢模式发生器（CPG）在整个发育过程中都位于CN X水平的延髓尾部，而肺CPG的位置在变态后幼虫中更靠前，位于CN VII水平。体内和体外研究均揭示了与鳃和肺通气相关的两种不同的神经爆发模式。在体内鳃通气和体外虚构鳃通气期间，观察到CN V、VII、X的顺序激活，而在肺通气和虚构肺呼吸期间，这些神经活动以及SN II表现出更同步的激活爆发模式。
