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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)
Temperature effects on extracellular acid-base status in terrestrial poikilotherms are well known. Comparatively less is known concerning the time course of acid-base responses to prolonged changes in temperature. In this study, two questions were addressed: (1) what is the time course of acid-base responses to a temperature change of 5 days duration in(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)
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)
Reptiles increase ventilation during hypercapnia at a constant temperature. In this study, the contributions of vagal vs non-vagal receptors to CO2 ventilatory responses were investigated in 16 sedated Alligator mississippiensis (25 mg/kg pentobarbital; 3 days prior to data collection). Four animals served as controls to assess the effects of time and/or(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)
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)
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)
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)
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)