Lymphatic innervation.

Bovine mesenteric lymphatic vessels have nerves in their walls which in response to field stimulation cause an increase in frequency of spontaneous lymphatic contractions and this could be blocked by alpha-antagonists. When vessels were loaded with [3H]-noradrenaline, 3H-efflux was increased in response to field stimulation and this was potentiated by alpha 2-antagonists and depressed by alpha 2-agonists. Electrical activity in these vessels consisted of a single action potential which preceded each contraction. Mean resting potential was -61 mV +/- 5.7 (SD). Stimulation of postsynaptic alpha-receptors caused a depolarization accompanied by a decrease in membrane conductance while beta-receptor stimulation had the opposite effect. Lymphatic noradrenergic nerves appear to have a role in the living animal since stimulation of the sympathetic chain in anaesthetized sheep increased popliteal efferent lymph flow and this could be blocked by alpha-adrenergic blockers.