Inhibitory effects on fast sympathetic rhythms.

In decerebrate cats, the effects of barbiturate anesthesia and of pulmonary afferent activity (produced by lung inflation) on fast (ca. 10/s) rhythms in sympathetic efferent discharges (cervical sympathetic and splanchnic) were analyzed. These inhibitory influences, in addition to reducing overall activity, eliminated or drastically reduced the highest frequency oscillations. Barbiturate anesthesia also markedly reduced high frequency oscillations (ca. 100/s) in phrenic discharge. Apparently, then, the occurrence of fast neural rhythms is dependent on the level of tonic excitatory activity.