Nucleus tractus solitarius lesions elevate pulmonary arterial pressure and lymph flow

The effects of lesions of the nucleus tractus solitarius (NTS) on pulmonary vascular pressure and pulmonary lymph flow were investigated in 6 halothane-anesthetized sheep. After lesions of the NTS were created using bilateral thermocoagulation, pulmonary artery pressure rose to 150% of baseline and remained elevated for the 3-hour duration of the experiment. Systemic and left atrial pressures did not change. Pulmonary lymph flow doubled within 2 hours; the lymph-plasma protein ratio was unchanged from baseline. Sham NTS lesions and lesions lateral to NTS produced no changes. These experiments demonstrate that lesions of the central nervous system can alter pulmonary vascular pressures and transcapillary fluid flux independently of effects upon the systemic circulation. These findings may have relevance for the understanding of neurogenic pulmonary edema in humans.