COORDINATION OF CONTRACTILE ACTIVITY IN GUINEA-PIG MESENTERIC LYMPHATICS

1. Intraluminally perfused lymphatic vessels from the mesentery of the guinea-pig were examined in vitro to investigate their contractile ac tivity and the co-ordination of this activity between adjacent lymphan gions. 2. Lymphangions constricted at fairly regular intervals and exh ibited 'refractory' periods of up to 3 s during which constrictions di d not occur. 3. The contractile activity of adjacent lymphangions was highly co-ordinated. 4. The smooth muscle was found to be continuous b etween the adjacent lymphangions for the majority of valve regions exa mined morphologically (52 of 63 preparations). 5. Mechanical and elect rical coupling between adjacent lymphangions was indicated, as some ly mphangions underwent transient dilatations just prior to constriction, whereas direct electrophysiological measurements showed that the smoo th muscle of most adjacent lymphangions was electrically coupled acros s the valve (15 out of 20 pairs of lymphangions). 6. It is concluded t hat perfused lymphangions of guinea-pig mesenteric lymphatic vessels r hythmically constrict, with the contractile activity of adjacent lymph angions highly co-ordinated. The findings also indicate that transmiss ion of both mechanical and electrical signals between the adjacent lym phangions contribute to the co-ordination of their contractile activit y.