| Abstract: | We studied isolated bovine mesenteric lymphatics to investigate the pharmacological properties of the postjunctional-adrenoceptors. Rings of the lymph vessels were mounted for isometric tension recording in organ chambers filled with Krebs-Ringer bicarbonate solution. The lymph vessels contracted when exposed to phenylephrine and clonidine. The relative sensitivity of the vessels to clonidine was larger than to phenylephrine. Yohimbine was a competitive antagonist against phenylephrine and clonidine in the lymph vessels. Prazosin caused a parallel shift to the right of the dose-response curve to phenylephrine, and not to clonidine in the vessels. The Schild's plot for yohimbine in the lymph vessels suggests that the presence of both alpha 1- and alpha 2-like adrenoceptors on lymphatic smooth muscle cells. |
