Gallamine and vagotomy enhance respiratory modulation of reticular units.

Respiration related units ( RRU ) were recorded in the brainstem of cats with spinal transection at the C7-Th 1 level and breathing N2O. The proportion of RRU in several structures was compared in control and in 3 experimental groups: (1) paralyzed with gallamine triethiodide; (2) vagotomized; and (3) both vagotomized and paralyzed. After gallamine, RRU percentage was multiplied by 3 in the bulbo-pontine reticular formation (RF) and as much as 20 in the mesencephalic RF. Vagotomy multiplied RRU proportions by 2 in the bulbo-pontine RF, by 12 in the mesencephalic RF and by 3 in the pneumotaxic complex (nucleus parabrachialis medialis ( NPBM ) and K olliker -Fuse (KF) nucleus). The effects of gallamine and vagotomy were not additive. Gallamine still increased proportion of RRU in the RF after vagotomy showing that the gallamine effect is not vagally mediated; this was in contrast to the previously reported suppression by vagotomy of phrenic discharge facilitation induced by gallamine. The total number of firing units in the RF was not modified by gallamine or vagotomy. It is concluded that the respiratory modulation of reticular neurons is selectively enhanced by gallamine and vagotomy through two independent mechanisms.