Does the autonomic nervous system regulate whole-body lymph flow?

We compared whole-body lymph flow responses with and without the autonomic nervous system intact in pentobarbital-anesthetized, acutely nephrectomized dogs. We measured left thoracic duct lymph flow, lymph and plasma protein concentrations, arterial and venous pressures, heart rate, and hematocrit in eight intact and six ganglion-blocked (hexamethonium, 15 mg/kg iv) animals. Ganglionic blockade lowered arterial pressure and heart rate but did not change lymph flow rate or the other variables. In the control and blocked groups at 30-min intervals, isotonic saline, lactated Ringer, and Dextran 70 solutions were serially infused, followed by hemorrhage and reinfusion of shed blood. Infusions or withdrawals were equal to 2% of body weight and were induced over 5-min intervals followed by 25 min of recovery. Lymph flow generally increased to a peak 5–7 min after each infusion was ended and then decayed back toward preinfusion levels; the extent of the rise in lymph flow, the time of the peak flow, and the extent of decay after the peak were unaffected by autonomic blockade. The absolute lymph flow rates in response to the infusions, hemorrhage, or blood infusion were not appreciably altered by ganglionic blockade. Thus the present studies provide little support to the hypothesis that the autonomic nervous system contributes to whole-body lymph flow.