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The ventilatory control system utilizes a variety of sensory receptor groups, including chemoreceptors and mechanoreceptors, to provide feedback concerning the status of controlled variables. Most ventilatory responses to altered receptor inputs generally involve a complex interaction between several receptor groups, central integrative mechanisms, and(More)
An in vitro brainstem-spinal cord preparation from adult turtles was used to study mechanisms underlying the episodic breathing pattern in poikilothermic vertebrates. The preparation (1) generates a stable, episodic burst pattern in cranial motoneuron discharge lasting several days; and (2) is similar to discharge patterns in vivo that are synchronous with(More)
Exposure of anesthetized paralyzed vagotomized peripherally chemodenervated cats to hypoxia results in initial depression and subsequent loss of the phrenic neurogram. To determine whether hypoxic respiratory depression results from the inhibition of respiratory premotor neurons by bulbospinal neurons of the Bötzinger complex (Böt-E neurons), extracellular(More)
We determined the effects of serotonin (5HT; 6 concentrations ranging from 0.005 to 500 microM) pressure microinjection into the hypoglossal (XII) motor nucleus (100-500 nl; pH = 7.2-7.4) on XII whole nerve activity and reflex response to upper airway negative pressure in 15 decerebrated, vagotomized, paralyzed and artificially ventilated cats. Increasing(More)
1. Respiratory interneurones in the C4-C6 segments of the spinal cord have only recently been described; until now their projections and connections were not known. We investigated expiratory interneurones in the C5 spinal segment, using antidromic mapping to trace their projections and spike-triggered averaging to test their synaptic connections with(More)
Axonal projections and synaptic connectivity of upper cervical inspiratory neurons (UCINs) were investigated in anaesthetised cats to clarify their role as propriospinal respiratory interneurons. Antidromic mapping showed axonal collaterals near phrenic and intercostal motonuclei. Of the UCINs tested, 37% had collaterals at T3-4; 55% had ipsilateral(More)
The episodic breathing pattern in many reptiles consists of two or more clustered breaths separated by variable non-ventilatory periods. This pattern is commonly postulated to result from oscillations in lung and/or blood PO2 or PCO2 via chemoreceptor feedback. We tested this hypothesis by monitoring breathing pattern in: (1) awake, undisturbed alligators(More)
The responses of 57 upper cervical inspiratory neurones to single shock stimuli applied to the ipsilateral cervical vagus nerve were recorded using peri-stimulus histograms in 19 cats. Many (47%) of the histograms showed a late latency (17.9 +/- 3.4 ms; mean +/- S.D.) broad peak following the stimulation preceding a similar peak in the histogram for the(More)
Although bulbospinal, expiratory neurones of the Bötzinger complex (BOT E-AUG) are known to have monosynaptic inhibitory connections to many bulbospinal respiratory neurones, their connections to propriobulbar respiratory neurones have not been so well characterized. We stimulated BOT E-AUG neurones with trains of pulses, and found an inhibition of(More)
Bötzinger complex (BOT) augmenting expiratory neuron efferent connection are well established, but little is known concerning the afferent neural projections to BOT. The dorsal (DRG) and ventral (VRG) respiratory groups were extensively searched in 17 pentobarbital anaesthetized cats for inspiratory neurons that were anti-dromically activated from BOT. Only(More)
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