The effects of norepinephrine and acetylcholine in the vas deferens from normal and diabetic rats: influence of ouabain and verapamil.

In vas deferens from acute and chronic diabetic rats a hypersensitivity to norepinephrine and acetylcholine was observed. The hypersensitivity to norepinephrine was markedly reduced by treatment with ouabain or verapamil. On the contrary, the response to acetylcholine was not modified by ouabain in the same concentration, but was inhibited by verapamil. Under normal conditions, ouabain and verapamil did not modify the stimulatory effect of either norepinephrine and acetylcholine; however increase of extracellular potassium concentrations potentiated the action of norepinephrine. The results suggest that ouabain-sensitive (Na+ + K+)ATPase exists in the rat vas deferens. In diabetic animals, the supersensitivity to norepinephrine is associated with an increase in membrane permeability to calcium ions that could be related to hypersensitivity of the enzyme. Under normal conditions it is possible to mimic the hypersensitivity to norepinephrine through an increase in the extracellular potassium concentration.