Nervous modulation of spontaneous contractions in bovine mesenteric lymphatics.

1. Spontaneous isometric contractions were measured in 2 cm segments of bovine mesenteric lymphatics. 2. Field stimulation at 0.25, 1 anf 4 Hz increased the frequency of contraction. 3. Tetrodotoxin 3 x 10(-6) M blocked the response to electrical stimulation. 4. Phenoxybenzamine 3 x 10(-7) M converted the excitatory effect of stimulation to an inhibitory one. 5. Propranolol 3 x 10(-7) M potentiated the excitatory response to stimulation at 1 and 4 Hz. 6. Field stimulation was without effect in the presence of propranolol and phenoxybenzamine together. 7. Cocaine potentiated the response to stimulation at 0.25 and 1 Hz. 8. Atropine 3 x 10(-7) M failed to block the excitatory effect. 9. Field stimulation at 0.5 and 1 Hz increased the frequency of spontaneous contractions and propulsion of fluid by 8 cm cannulated segments of lymphatic. 10. The results suggest that bovine lymphatic vessels have a noradrenergic innervation which is capable of controlling lymph flow.