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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)
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)
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)
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)
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)
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)
The effects of body temperature (Tb) on pulmonary stretch receptor (PSR) and CO2-sensitive intrapulmonary chemoreceptor (IPC) response characteristics may have important effects on ventilatory control in reptiles. In this study, three questions were addressed: (1) what are the effects of Tb on PSR and IPC responses to airway pressure (Paw) and lung CO2(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)