FIG. 2.

Comparison of the effects of pharmacological blockade of NO and histamine production on high flow-induced (5 cm H₂O of imposed flow gradient) relaxation and contractile inhibition in adult (9-mo) and aged (24-mo) MLVs. (A) Lymphatic tone index; (B) contraction amplitude; (C) contraction frequency; (D) fractional pump flow. Control, control MLVs after overnight culture; L-NAME, same control vessels after subsequent acute pharmacological blockade of NO production by the NOS nonspecific blocker, L-NAME (100 μM); a-MHD, MLVs after overnight pharmacological blockade of histamine production by the HDC-specific blocker, α-MHD at 10 μM; a-MHD+L-NAME, same α-MHD-treated vessels after subsequent acute pharmacological blockade of NO production by the NOS nonspecific blocker, L-NAME at 100 μM. “*” indicates significant difference (p < 0.05) between lymphatic contractile parameters within each treatment group at no-flow and at conditions of 5 cm H₂O of imposed flow gradient. “+” indicates significant difference (p < 0.05) between lymphatic contractile parameters in any treatment group and the control group. “Δ” indicates significant changes (loss or gain of statistical significance, p < 0.05) of lymphatic contractile parameters in any pair of values in treatment/flow combinations within the aged MLV group when compared to similar pairs of values in the adult MLV group. 9-mo, 9-month-old; 24-mo, 24-month-old.