Possible embryogenetical differences of the dog venous system in sensitivity to vasoactive substances.

Using isolated dog veins, we examined whether correlations exist between the regional differences in sensitivity to drugs and their embryogenesis. Twelve different veins were dissected. In the analysis, the data obtained previously for the inferior vena cava were also included. Spiral strips were prepared and the contractile responses to cumulative application of norepinephrine (NE), 5-hydroxytryptamine (5-HT), histamine (Hist) and acetylcholine (ACh) were recorded isometrically. For each drug, a histogram was drawn by stacking the overlapping ranges (mean +/- S.E.) of the pD2, value for each vein. The histogram indicated the number of veins which could share the same pD2 value. We obtained the following results: (1) Veins of the body wall had high sensitivity to NE (pD2 greater thn 6.40) and 5-HT (pD2 greater than 6.60) and veins of the intestinal system, except for the splenic vein, were not so sensitive to NE and 5-HT, but exhibited high sensitivity to Hist (pD2 greater than 4.60); (2) the middle segment of inferior vena cava responded similarly to portal and mesenteric veins; (3) the responses of splenic vein to the agents used were quite different from those of portal and mesenteric veins. These results suggest possible correlations between the responsiveness of venous smooth muscles and embryogenesis of the venous system.