Medullary expiratory neurons in the decerebrate rat: an intracellular study

Inhibitory connections among rostral medullary expiratory neurones detected with cross-correlation in the decerebrate rat*

“…In general we found expiratory neurones where others have found them Saether et al 1987;Zheng et al 1991b;Zheng et al 1992). The E-DEC neurones shown to be inhibitory were located rostral to the obex, and most were within or near the region where we found inhibitory E-AUG neurones.…”

Caudal expiratory neurones in the rat

“…However, this technique does not distinguish between inspiratory and expiratory neurones. Saether et al (1987) has found expiratory bulbospinal neurones but did not describe their discharge patterns and Zheng et al (1992b) has reported that 0 of 19 augmenting pattern expiratory neurones could be activated antidromically from the spinal cord, but three out of three constant-pattern neurones could be activated from the ipsilateral side. Finally, Sun et al (1996) has found that the stem axons of four out of seven neurones stained with neurobiotin coursed medially and crossed the midline.…”

“…Therefore the medullary neurones that provide expiratory drive to respiratory muscles, either directly in the case of cranial motoneurones or indirectly via bulbospinal projections to spinal respiratory motoneurones, must also be coordinated to the respiratory cycle. These medullary expiratory neurones are thought to be located in the caudal ventral respiratory group in the rat (Ezure et al 1988;Saether et al 1987;Zheng et al 1991;Zheng et al 1992b) a region analogous to that in cats (Ezure 1990), and neurones there have been shown to have the appropriate discharge patterns (Schwarzacher et al 1991;Zheng et al 1991).…”

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

“…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 from our laboratory, similar procedures involving timed application of inflations have been done in the decerebrate cat (10, 11); now, in the present study, such procedures have been applied in the decerebrate rat.…”

“…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.…”