Respiratory reflexes from the trachea and bronchi of the cat

Abstract

Although considerable work has been carried out on respiratory reflexes from the lungs, less attention has been paid to the trachea and bronchi. Having completed an analysis of afferent nerve fibres from the tracheobronchial tree of the cat (Widdicombe, 1954 a), it was desirable to identify the reflexes from this area, so that the functions of each afferent fibre group could be distinguished. This paper describes the experiments on tracheobronchial reflexes. The best known of these is the cough reflex which, although of obvious physiological and pathological importance, has been little investigated experimentally.As well as the cough reflex another tracheobronchial reflex has been described. Hammouda & Wilson (1936) showed that changes in the tracheal diameter of the dog caused a slowing of respiration. This reflex has been investigated in cats. METHODSCats have been used, anaesthetized with intraperitoneal sodium pentobarbitone (32 mg/kg) or with intravenous chloralose (60 mg/kg), the latter after induction with ethyl chloride and ethyl ether. Decerebrate cats were used for one series of experiments; these were prepared under ether anaesthesia and, as with chloralose, no experimental observations were made until sufficient time had elapsed for the volatile anaesthetics to be blown off (30-60 min). A tracheal cannula was inserted.Respiration was usually recorded with the body plethysmograph described by Dawes, Mott & Widdicombe (1951); the volume changes of the animal's body from the neck downwards were registered by a float spirometer which wrote upon a smoked drum. In some experiments a spirometer was used in which the float was attached by its centre of rotation to the moving arm of a potentiometer; the latter was connected to a potential source and the voltage changes from the moving arm were amplified and recorded on a direct-coupled cathode-ray oscilloscope; the response was very nearly linear.In cats which had had a thoracic operation it was often inconvenient to enclose the animal in the plethysmograph, and the respiration was recorded using a modification of the method of Donald & Christie (1949) for man (Fig. 1). The cat breathed through inspiratory and expiratory valves (VI and VE) of small dead space and resistance; inspired and expired airs were separated by a tbin-walled rubber bag and the volume changes of the system recorded by a float spirometer.

What is cough and what should be measured?

“…Spontaneous and induced coughs are associated with the sensation 'urge-to-cough', which may have a lower threshold than cough itself, and usually precedes it [8,10,12,14] The neural connections for cough between the cortex and the brainstem have not been worked out. Decerebrate animals can cough vigorously with an irritant stimulus [18], so at most the cortex can induce or facilitate cough (or inhibit it). It seems likely, although unproven, that the cortex can switch on or off the cough reflex, or else modulate the strength of a stereotyped and complex pattern of cough based on the brainstem neural pathways [13].…”

Voluntary and reflex cough and the expiration reflex; implications for aspiration after stroke

“…This has inspiratory, compressive and expulsive phases. It originates in the cerebral cortex; decerebrate animals have a vigorous RC [17] but, M A N U S C R I P T…”

“…This is important, not only because the tests become more sensitive in assessing the risk of aspiration, but because they show that cough and its different types are very complex motor activities (which seems obvious). This is well established for healthy experimental animals [13,17] and humans [10,11,12].…”

Potent cough suppression by physiologically active substance in human plasma

“…Recent studies identified Aδ afferent neurons as essential in cough in the anesthetized guinea-pig, and the term "cough receptors" (Widdicombe 1954a(Widdicombe , 1954b was re-introduced (Canning et al 2004;Mazzone et al 2005Mazzone et al , 2009) for the following reasons. (i) Conduction velocity of "cough receptors" is much slower than that of rapidly adapting stretch receptors (RARs) or slowly adapting stretch receptors (SARs) (Bergren and Sampson 1982;Ho et al 2001;Canning et al 2004;Undem et al 2004), but much faster than that of C-fibers (Riccio et al 1996;Ho et al 2001).…”