Differentiation of respiratory reflexes by electrical stimulation and cold blockade of the vagus nerve in rabbits.

Using cold blockade of conduction in the myelinated nerve fibres respiratory effects were studied evoked by centripetal stimulation of the vagus nerve. The experiments were carried out on rabbits under general anaesthesia with halothane and with artificial ventilation. The vagus nerves were cut in the neck and one of them was adapted for stimulation of its proximal part. Electrical stimulation was applied in expiration using impulse frequency 50/sec. The direction of the response (i.e. prolongation or shortening of the expiration phase during stimulus application) served for determination of the excitation threshold of the afferent fibres from slowly-adapting and rapidly-adapting pulmonary mechanoreceptors. It was found that the conduction in the afferent fibres from the slowly-adapting pulmonary receptors could be blocked selectively with cooling temperatures 8-10 degrees C.