ELECTRICAL-STIMULATION OF PNEUMOTAXIC CENTER - ACTIVATION OF FIBERS AND NEURONS

Electrical stimulations of the pneumotaxic center can result in a phas e-switch from neural inspiration to expiration or the reverse. Termina tions of inspiration are also obtained from many loci ventral to the p neumotaxic center. We hypothesized that responses to some stimulations reflect an activation of fibers rather than neurons. Studies were con ducted in decerebrate, vagotomized, paralyzed and ventilated cats. Act ivities of the phrenic and triangularis sterni nerves were recorded. A multibarreled pipette was inserted into the rostral pons. Electrical stimulation was delivered through two barrels; another contained kaini c acid to destroy neurons. The threshold current for producing inspira tory termination was not altered in most regions following the injecti ons of kainic acid. However, stimulation of neurons did appear to unde rlie the premature onset of phrenic activity. In addition, neurons in medial pontile regions regulate triangularis sterni activity. We concl ude that some functions ascribed to the pneumotaxic center are, in fac t, subserved by neurons in other regions of the central nervous system .