With cats anaesthetized with
sodium pentobarbital we studied how
veratrine-induced reflexes interact with
cough.
Cough was elicited by mechanical stimulation of tracheobronchial mucosa and its intensity was evaluated from the changes in oesophageal pressure.
Veratrine injected intravenously produced apnoea,
bradycardia and long-lasting
hypotension. With each dose the intensity of
cough was significantly decreased during the apnoea. When the mechanical stimulus was repeated during the breathing following apnoea with remaining
hypotension,
cough intensity parameters were not changed from control.
Veratrine injected intracardially caused
bradycardia,
hypotension, and decreases in respiratory rate and tidal volume. The intensity of
cough elicited just after injection of
veratrine was also significantly decreased. We suggest that
veratrine-induced reflexes depress the
cough reflex mainly by inhibitory reflexes arising from cardiac receptors. The inhibition of
cough is probably mediated indirectly via the inhibition of medullary respiratory neurons.