Development of short-term potentiation of respiration

Development of short-term potentiation (STP) of respiration, which leads to the respiratory 'afterdischarge', was studied in anesthetized, paralyzed, vagotomized and glomectomized cats. Phrenic nerve activity was used as an index of respiratory output. Respiratory output was increased and the potentiating mechanism activated by electrical stimulation of a carotid sinus nerve (CSN). Development of STP was determined from the magnitude of potentiation after various durations (0 to 60 sec) of stimulation. The average time constant (TC) for the development of the potentiation was 9 sec, whereas the TC for its decay (afterdischarge) was 46.1 +/- 3.9 sec. The magnitude of potentiation is dependent upon the number of pulses in the stimulus train. We conclude that the development of short-term potentiation of respiration is relatively slow but much faster than the decay, or afterdischarge. We suggest that the slow increase of respiration during a stimulation and the decay afterwards are due to a common mechanism, short-term potentiation of neural activity in respiratory control pathways.