Respiratory cycle timing and fast inspiratory discharge rhythms in the adult decerebrate rat

Abstract

Marchenko, Vitaliy, Antonio R. Granata, and Morton I. Cohen. Respiratory cycle timing and fast inspiratory discharge rhythms in the adult decerebrate rat. Am J Physiol Regul Integr Comp Physiol 283: R931-R940, 2002. First published June 27, 2002 10.1152/ajpregu.00117.2002In supracollicular decerebrate paralyzed adult rats, neural respiration was monitored by bilateral phrenic recordings. In the study of respiratory cycle timing, the effects of vagal afferent input (lung inflation) on respiratory phase durations resembled those seen in decerebrate cats. 1) Withholding lung inflation during neural inspiration (I) produced lengthening of I phase duration by 46% (mean, n ϭ 11). 2) Maintaining lung inflation during neural expiration (E) produced lengthening of E phase duration by 112% (mean, n ϭ 4). In the study of fast rhythms in inspiratory discharges, phrenic nerve autospectra and bilateral (left-right) phrenic coherences in 16 rats revealed two types of fast rhythm: 1) highfrequency oscillation (HFO), which had significant coherence peaks (n ϭ 9, range 106-160 Hz, mean 132 Hz); and 2) medium-frequency oscillation (MFO), which had autospectral peaks but no distinct coherence peaks (n ϭ 11, range 46-96 Hz, mean 66 Hz). These rhythms resembled MFOs and HFOs in the decerebrate cat, but the modal frequency range was about twice as large. In addition, these frequency values differed markedly from the 20-40 Hz of the rhythms found in earlier studies in neonatal in vitro preparations; the difference may be due to developmental immaturity. phrenic; vagal afferents; high-frequency oscillations; medium-frequency oscillations; spectral analysis IN RECENT YEARS, much of the research on neurogenesis of respiratory rhythm has been performed on in vitro preparations (most commonly obtained from neonatal rats), such as the en bloc (isolated brain stem-spinal cord) preparation and the medullary slice preparation (1). To help interpret observations made in vitro, it would be useful to make comparisons with in vivo observations. Although the major portion of earlier in vivo studies had been done in the cat (3, 32, 36), a number of in vivo studies have also been done in the rat (14,15,34,(41)(42)(43) and therefore might furnish suitable comparisons.The present paper deals with aspects of two broad areas of interest in both in vitro and in vivo studies: 1) the temporal structure of the overall respiratory cycle, such as the durations of the inspiration (I) and expiration (E) phases; and 2) the short-term timing relations between different inspiratory (phrenic) neural activities, as indicated by fast rhythms in their discharges.With respect to respiratory cycle timing, publications from one laboratory have reported the effects of lung afferent input (inflations) on respiratory cycle timing in the en bloc preparation with lungs attached: inflations delivered during the E phase produce prolongation of that phase (27), whereas inflations delivered during the I phase result in shortening of that phase (28,29). In previous in vivo studies...

Time-Frequency Representation of Inspiratory Motor Output in Anesthetized C57BL/6 Mice In Vivo

“…These investigations have revealed fast oscillations in inspiratory nerve activities in both anesthetized and decerebrate rats in vivo, with the power spectrum most often characterized by a single spectral peak in either the MFO or HFO range (dual spectral peaks were rarely encountered). Furthermore, the peak frequencies associated with HFO activity were reported to be slightly higher in adult rats than those previously observed in other mammals; based on these recent observa-tions, the upper limit of the original HFO range has been extended to ϳ160 Hz (Kocsis and Gyimesi-Pelczer 1997;Marchenko et al 2002). Because the mouse is rapidly becoming a valuable model for studying the contribution of genetic factors in respiratory control (see recent review by Tankersley 2003), and to our knowledge, spectral composition of inspiratory-related activity in adult mouse has not yet been evaluated, we conducted this study, in part, to investigate the presence and location of fast oscillatory rhythms in inspiratory motor discharges in adult mouse in vivo.…”

“…Because it has been suggested that spectral content in inspiratory motor discharges may change over the course of the inspiratory burst (Bruce 1986(Bruce , 1988Christakos et al 1989Christakos et al , 1991Cohen et al 1987b;Marchenko et al 2002;Richardson 1988;Richardson and Mitchell 1982;Schmid et al 1990;Webber 1989), time-frequency analyses using a generalized TFR with the SPWD kernel were performed on recordings of diaphragm EMG activity, phrenic nerve discharge, and hypoglossal nerve discharge to evaluate the time-varying (i.e., dynamic) features of spectral activity (see Time-frequency spectral analysis: SPWD). There existed, however, two possible outcomes regarding the TFR of the inspiratory motor discharges: 1) the inspiratory motor discharges would exhibit fast oscillatory components that are continuous during the inspiratory burst (i.e., time-invariant) or 2) the inspiratory motor discharges would exhibit fast oscillatory components that exist at particular times during the inspiratory burst (i.e., time-varying).…”

“…Although prominent oscillations in inspiratory-related discharges have been identified in all mammals studied thus far, only a limited number of investigations have focused on adult rodents (Kocsis and Gyimesi-Pelczer 1997;Marchenko et al 2002). These investigations have revealed fast oscillations in inspiratory nerve activities in both anesthetized and decerebrate rats in vivo, with the power spectrum most often characterized by a single spectral peak in either the MFO or HFO range (dual spectral peaks were rarely encountered).…”

“…These conventional spectral analysis methods assume that the signal being analyzed is stationary (i.e., the fast oscillatory components do not change with time), which is not the case for most biological signals, which exhibit varying degrees of nonstationarity. In fact, some studies have used power spectral analyses (using FFT algorithms) to compare spectral content of early versus late segments of the inspiratory burst (e.g., 1st half vs. 2nd half) (Bruce 1986(Bruce , 1988Christakos et al 1989Christakos et al , 1991Cohen et al 1987b;Marchenko et al 2002;Schmid et al 1990;Webber 1989) or have stepped through the inspiratory burst with a 250-ms window in small steps (e.g., 1/16 s) (Richardson 1988;Richardson and Mitchell 1982) in an attempt to show that spectral content may change during inspiration. Although these studies have revealed changes in power and/or frequency of spectral peaks in the MFO and/or HFO ranges during inspiration, the segmenting procedures used may have been inadequate to produce data segments exhibiting stationarity, which is the underlying assumption for conventional spectral analyses.…”

“…In the respiratory neural control system, it has long been recognized that fast oscillatory rhythms are present in inspiratory-related muscles, nerves, and neurons (recently reviewed by Funk and Parkis 2002) and that these fast rhythmic oscillations provide an index of inspiratory-phase short-time-scale synchronization (Cohen et al 1987b;Dittler and Garten 1912;Gasser 1928;Sica et al 1991). Initial investigations of these fast oscillatory rhythms used visual observation or auto-and cross-correlation techniques to identify fast oscillations in inspiratory-related discharges in the range of 50 -100 Hz (e.g., Cohen 1973;Dittler and Garten 1912;Gasser 1928;Mitchell and Herbert 1974); however, more recent studies have used power spectral analyses [using predominantly fast-Fourier transform (FFT) algorithms] that have revealed spectral peaks in two ranges: 20 -50 Hz (Cohen et al 1987b;Richardson and Mitchell 1982), designated as medium frequency oscillations (MFO; Cohen et al 1987b), and 50 -150 Hz, designated as high-frequency oscillations (HFO; Cohen et al 1987b).Although prominent oscillations in inspiratory-related discharges have been identified in all mammals studied thus far, only a limited number of investigations have focused on adult rodents (Kocsis and Gyimesi-Pelczer 1997;Marchenko et al 2002). These investigations have revealed fast oscillations in inspiratory nerve activities in both anesthetized and decerebrate rats in vivo, with the power spectrum most often characterized by a single spectral peak in either the MFO or HFO range (dual spectral peaks were rarely encountered).…”