Respiratory activity of the pons and its influence on breathing in the guinea pig.

The localization of respiratory activity in the pons of the anaesthetized guinea pigs has been studied. The respiration related units were localized in/or close to the following anatomical structures: nucleus parabrachialis, nucleus trigemini motorius and nucleus reticularis pontis caudalis. The influence of the pontine respiratory activity on the pattern of breathing was studied by the use of a reversible pharmacological block (local anaesthetic) of these structures. The application of lignocaine to all investigated sites of the pons caused the prolongation of both respiratory phases, then an effect comparable to vagotomy. In the vagotomized animal the focal block of nucleus parabrachialis has never produced apneusis (pronounced prolongation of inspiration and very short lasting expiration). Since the removal of some pontine structures involved in the breathing control caused the depression of respiration, we concluded that the respiratory activity of the pons in the guinea pigs exerts an excitatory influence on the rhythm generating mechanism in this animal.