Aktionspotentiale atmungssynchron entladender Neurone der Medulla oblongata beim Husten

Stimulus response latency of cough and expiration reflex depends on breathing in the rabbit

Expiration reflex and cough may have distinct afferent pathways and/or central integrative mechanisms that may both result in different stimulus response latencies. A newly described method that uses a punctuate mechanical tracheal stimulus to provoke defensive ventilatory reflexes should allow the stimulus response latency to be calculated with reasonable accuracy. The aim of the study was to test whether cough and expiration reflex have different stimulus response latencies. Four hundred and sixty one mechanical tracheal stimulations (50-300 msec) were performed in 21 anesthetized, tracheotomized rabbits. Twenty three percent stimulations (108) provoked a cough reflex and 37% an expiration reflex (171). The individual mean stimulus response latency was computed for each reflex, calculated from stimulus onset to earliest detectable change in ventilatory flow. Cough reflex latency was significantly shorter in inspiration compared to expiration (257±19 msec vs 391±61 msec; p=0.01). In contrast, the expiration reflex latency was significantly shorter in expiration compared to inspiration (210±11 msec vs 329±29 msec, p=0.003). It is concluded that the within breath dependence of the difference in stimulus response latency between cough and expiration reflex is more likely to express different brainstem mechanisms but difference in afferent fibres may not be excluded.

Anxiolytic-like properties of fominoben

Fominoben, a centrally acting antitussive, has been shown recently to bind to the brain benzodiazepine binding site and to antagonize pentylenetetrazol-induced seizures. The present study reports the ability of fominoben to produce anti-anxiety effects analogous to diazepam in a mouse exploratory model for anxiolytics. This action of fominoben was blocked by Ro15-1788, a benzodiazepine receptor antagonist, implicating a brain benzodiazepine binding site in this anxiolytic action of fominoben.

The activity of respiratory neurons before and during panting in the cat

The effects of heating the preoptic/anterior hypothalamic (PO/AH) region on medullary respiratory neurons were studied in urethane-anesthetized, spontaneously breathing cats. The efferent phrenic nerve discharge or the pneumotachogram served as an indicator of central respiratory periodicity. In each animal, heating of the PO/AH area caused panting, defined as an increase of respiratory rate over 100 breaths per minute. During polypnea similar changes in the discharge patterns of both inspiratory and expiratory neurons were observed. There was a significant decrease in the duration of the discharge phase and the number of impulses per burst so that a reciprocal relationship existed between these parameters and respiratory rate. However, the average impulse frequency within a burst was higher during panting and could be shown to be a linear function of respiratory rate. Due to the concomitant decrease in inspiration and expiration times, the average discharge frequency per cycle time also increased in both inspiratory and expiratory medullary neurons. For continuously discharging neurons which displayed a higher frequency during the inspiration period (frequency modulated discharge), the phasic linkage remained unchanged during polypneic panting. From our results it is concluded that local heating of the PO/AH region shifts the entire respiratory system to a higher level of activity which can be correlated with ventilatory changes during panting.