Release of norepinephrine by electrical field stimulation of collateral arteries from the hindlimb of the dog.
Studies were conducted comparing the electrical field-stimulated contractile response and endogenous norepinephrine overflow of developing collateral arteries to that of branch arteries from normal extremities. Norepinephrine overflow was measured by radioenzymatic assay. Experiments on collateral arteries were undertaken 6 weeks after occlusion of the femoral artery. Collateral arteries had a lesser contractile response at lower voltages of stimulation with a greater direct smooth muscle component. This occurred despite previously reported greater sensitivity to alpha-adrenergic agonists. Stimulated norepinephrine overflow was significantly greater despite a lower norepinephrine content. These findings may reflect alterations in local control of adrenergic neuronal transmission. The results also suggest an inefficient innervation of vascular smooth muscle by adrenergic nerve endings. Lack of difference between anterior tibial artery from unoccluded (normotensive) and occluded (hypotensive) extremities excluded the possibility that differences between collateral and normotensive branch arteries were due to hypotension alone.
D000818:Animals; D003097:Collateral Circulation; D004285:Dogs; D004558:Electric Stimulation; D005263:Femoral Artery / Q000502:physiology*; D006614:Hindlimb / Q000098:blood supply; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*
D009638:Norepinephrine