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W A Karczewski

Publications and source records attributed to W A Karczewski.

28 records · Page 2Linked to original sources
PubMed1980

Inspiratory facilitatory and inhibitory vagal influences during apnoea in rabbits.

During hyperventilation apnoea in vagotomized, anaesthetized rabbits, paralyzed and artificially ventilated, the effects of electrical afferent stimulation of the vagus nerve on the provocation and inhibition of inspiratory activity were investigated. The experiments were repeated using hyperinflation or short-lasting inflation in nonvagotomized animals. It was found that the possibility of observing inspiratory facilitatory phenomena depended on the interrelationship between the frequency of impulses transmitted separately through the thick and thin myelinated fibres. The time constants of central summation of vagal information and the possibility of observation of the phenomena of inspiratory facilitation depended on the central respiratory drive changed by CO2 and temperature.

Animals↗
PubMed1976

Respiratory neurons of the ventral respiratory nucleus of the rabbit and their vagal connections.

The pattern of firing and responses to electrical stimulation of the ipsilateral vagus nerve were studied in respiratory neurons near the nucleus ambiguus (NA) in the region called "ventral respiratory nucleus". In 41 (out of 77) respiratory neurons orthodromic responses were recorded; the remaining neurons did not respond to stimulation. It is concluded that the NA neurons of the rabbit are not laryngeal motoneurons. Moreover, the short-latency excitatory response of some of these neurons, and long-latency inhibition of the other, suggest that NA neurons may be involved in the processing of vagal information.

Animals↗
PubMed1973

Responses of respiratory neurons of the rabbit to some excitatory and inhibitory stimuli.

The effects of an afferent stimulation of the vagus nerve, hypercapnia and hyperventilation on the discharges of pontine, medullary and phrenic respiratory neurons were studied. The responses were investigated in spontaneously breathing, lightly anaesthetized rabbits with intact vagi, and subsequently during artificial ventilation, after vagotomy and under surgical anaesthesia. We found that the patterns of activity of respiratory neurons depend upon the integrity of vagal conduction, pattern of ventilation and depth of anaesthesia, and that vagotomy and deep anaesthesia markedly modify, and sometimes even reverse, the responses of these neurons to respiratory stimuli. The pre-vagotomy type of response can be restored by stimulating the central end of a cut vagus nerve with standard pulses triggered by action potentials recorded simultaneously from the animal respiratory unit. The significance of these findings is discussed.

Animals↗
PubMedDate not supplied

Studies on the mechanism of obstructive sleep apnea.

Several observations indicate that the mylohyoid nerve (NV) may play a crucial part in the mechanisms of obstructive sleep apnea (OSA). The activity of this nerve normally counteracts the collapse of the upper airways during inspiration. Any reduction in this activity may thus facilitate the occurrence of apnoeic spells. We have studied the effects of ethanol and lung inflations on the activity of NV recorded along with the activities of phrenic and facial nerve in rabbits anaesthetised with chloralose-urethan, paralyzed with curare and artificially ventilated. Under the control conditions the NV exhibited phasic expiratory activity; after vagotomy and additional, inspiratory component was observed. Lung inflation strongly enhanced the expiratory activity of NV whereas both the phrenic and facial nerve activities (both phasic-inspiratory) were typically inhibited. An injection of 5 ml of 20% ethanol very strongly inhibited the NV activity. The results may confirm the importance of NV in the mechanism of OSA. The well-known fact that OSA patients are particularly sensitive to alcohol finds support in the response of NV activity to ethanol injection. The analysis of the patterns of discharges of the three outputs from the respiratory controller may additionally suggest that the Vth nerve nucleus is involved in the control of respiratory pattern.

Animals↗
PubMedDate not supplied

Cerebral blood flow in split-brainstem rabbits.

Cerebral blood flow (CBF), mean arterial pressure (MAP) and heart rate (HR) were recorded in anaesthetised, vagotomised, paralysed and artificially ventilated rabbits before and after a mid-sagittal section of the lower brainstem ("split-respiratory centre"). Splitting the medulla elicited first a small decrease and then an increase in CBF, a decrease in HR but no change in MAP. Hypoxia reduced CBF but did not modify MAP or HR. Hypercapnia did not significantly affect any of these parameters. It is concluded that a midline section of the rabbit's medulla and lower pons does not impair CBF and therefore the decrease in output from the respiratory controller, observed in split-brainstem animals, is not likely to be elicited by alterations in CBF.

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