A regional difference in the in vitro response of the rabbit vena cava to norepinephrine

1. Isotonic concentration-response curves were constructed for the contractile effects of norepinephrine (NE) in venous strips prepared from the caudal and rostral portions of rabbit vena cava; in some cases the venous strips were damaged by scraping their inner (endothelial) surface with a scalpel. 2. In both control and damaged venous strips, the rostral portions exhibited a higher affinity and a greater capacity of contraction to applied NE than caudal portions. 3. Such results might be explained by a difference in the distribution (or characteristics) of alpha-adrenoceptors and/or by a difference in the ratio of circular to longitudinal muscular elements in these two regions of the vena cava. 4. These findings should be considered when designing experiments aimed at determining the effects of alpha-adrenoceptor agonists on rabbit vena cava.