Subtype Composition and Responses of Respiratory Neurons in the Pre-Bötzinger Region to Pulmonary Afferent Inputs in Dogs

Abstract

. Subtype composition and responses of respiratory neurons in the pre-Bötzinger region to pulmonary afferent inputs in dogs. J Neurophysiol 93: 2674 -2687, 2005. First published December 15, 2004 doi:10.1152/jn.01206.2003. The brain stem pre-Bötzinger complex (pre-BC) plays an important role in respiratory rhythm generation. However, it is not clear what function each subpopulation of neurons in the pre-BC serves. The purpose of the present studies was to identify neuronal subpopulations of the canine pre-BC and to characterize the neuronal responses of subpopulations to experimentally imposed changes in inspiratory (I) and expiratory (E) phase durations. Lung inflations and electrical stimulation of the cervical vagus nerve were used to produce changes in respiratory phase timing via the Hering-Breuer reflex. Multibarrel micropipettes were used to record neuronal activity and for pressure microejection in decerebrate, paralyzed, ventilated dogs. The pre-BC region was functionally identified by eliciting tachypneic phrenic neural responses to localized microejections of DL-homocysteic acid. Antidromic stimulation and spike-triggered averaging techniques were used to identify bulbospinal and cranial motoneurons, respectively. The results indicate that the canine pre-BC region consists of a heterogeneous mixture of propriobulbar I and E neuron subpopulations. The neuronal responses to ipsi-, contra-, and bilateral pulmonary afferent inputs indicated that I and E neurons with decrementing patterns were the only neurons with responses consistently related to phase duration. Late-I neurons were excited, but most other types of I neurons were inhibited or unresponsive. E neurons with augmenting or parabolic discharge patters were inhibited by ipsilateral inputs but excited by contra-and bilateral inputs. Late-E neurons were more frequently encountered and were inhibited by ipsi-and bilateral inputs, but excited by contralateral inputs. The results suggest that only a limited number of neuron subpopulations may be involved in rhythmogenesis, whereas many neuron types may be involved in motor pattern generation.

Pontine respiratory activity involved in inspiratory/expiratory phase transition

“…The shape of the excitatory post-synaptic potentials (EPSPs) largely corresponded to the discharge pattern of the pontine IE phase-spanning neurons. This allows the suggestion that the medullary late-I neurons involved in IE phase transition (Richter 1982(Richter , 1996Cohen et al 1993;Haji et al 2002;Krolo et al 2005) receive synaptic input from the pontine IE phase-spanning neurons Cohen & Shaw 2004;Rybak et al 2004Rybak et al , 2008. The pontine and medullary post-neurons had comparable discharge pattern and voltage changes (figure 2e, f ).…”

Opioid-induced Respiratory Depression Is Only Partially Mediated by the preBötzinger Complex in Young and Adult Rabbits In Vivo

“…1) has been accepted as a functional marker for the preBC by investigators using various animal models. 23,24 The tachypneic response to a glutamate agonist emphasizes the importance of this area in respiratory pattern generation. The preBC was defined as the area where DLH caused the largest increase in respiratory rate or, when the increase was identical in two neighboring areas, the area where the tachypneic effect lasted longest (fig.…”

Pontine Mechanisms of Respiratory Control

“…BHR feedback from the expanded lung during inspiration initiates IOS via exactly the same mechanism: excitation of late-I and (67, 158, 206, 310, 311) and post-I neurons (157, 163, 310, 311, 322). Consistent with the balance theory KF-area-mediated activation of late-I neurons can be suppressed by BHR feedback.…”