Respiratory pattern formation in the isolated bullfrog (Rana catesbeiana) brainstem spinal cord

This study characterizes various patterns of motor output obtained from cra nial nerves V, VII, X, and XII of in vitro, saline-perfused, brainstem-spin al cord preparations of the American bullfrog (Rana catesbeiana). Motor out put indicative of fictive breathing was present in all preparations. In 17 of 26 preparations, fictive breaths were either evenly spaced or randomly d istributed, while in the remaining nine preparations fictive breaths occurr ed in episodes separated by relatively long periods of quiescence. With the exception of fictive breath duration in the non-episodic preparations and the instantaneous frequency of fictive breaths within episodes, all variabl es associated with fictive breathing were insensitive to changes in perfusi on saline pH. In addition to fictive breathing, a large number of other for ms of motor output were observed arising from these nerves. While the data suggest that the in vitro preparation is capable of producing a wide repert oire of motor patterns, similar to those seen in vivo, it was difficult, wi th the current protocol, to reliably produce any single pattern in spite of carefully regulated conditions. (C) 1998 Elsevier Science B.V. All rights reserved.