Relaxation of XXXX mesenteric lymphatics in response to transmural stimulation.

@entity2997 @entity1169 @entity4033 @entity1022 @entity2072 @entity3897 @entity291 @entity17268 @entity6114
The responses of isolated quiescent segments of @entity291 mesenteric lymphatics to 10-s trains of pulses (50 V for 0.3 ms at 2 Hz) administered transmurally have been studied using various drugs. Each train of pulses consistently produced a brief contraction that was completely blocked by @entity1022 , alpha-adrenoceptor antagonists, @entity17268 , and @entity2997 . @entity2072 potentiated the contractions. @entity6114 caused an increase in the basal tone, some spontaneous contractions, and an inhibition of contraction. The contraction was sometimes followed by a relaxation that could be of short duration or long lasting. Both types of relaxation were abolished by @entity1022 . @entity1169 reduced both types of relaxation, causing more suppression of the short type. Bretylium completely blocked the short type of relaxation and slightly reduced the long-lasting type. @entity4033 and @entity3897 had no effect on any of the responses. These findings suggest that the contraction resulting from transmural stimulation is due to the action of excitatory postganglionic sympathetic nerves. It is concluded that both types of relaxation occur mainly in response to beta-adrenergic inhibitory stimulation. The possibility of nonadrenergic inhibitory innervation in @entity291 mesenteric lymphatics is also discussed.
