Network vascular communication initiated by increases in tissue adenosine

Vascular communication of vasomotor signals appears to coordinate the distr ibution of tissue blood flow. This study was performed to determine whether elevated tissue concentrations of adenosine or nitric oxide could induce v ascular communicating signals. To test this, remote arteriolar responses we re tested when drugs were applied either directly to an arteriole (similar to 20 mu m diameter), or into the tissue in a region (with no vessels over 10 mu m in diameter) that was 500 mu m away from the arteriole and that bor e no defined relationship to the flow path of the remote arteriole. In anes thetized hamster cheek pouch (n = 25), or cremaster muscle (n = 10), remote arteriolar responses were measured in response to nitric oxide (NO) donors (10(-5) to 10(-3) M), adenosine (10(-5) to 10(-3) M), or papaverine (10(-5 ) to 10(-2) M) applied for 40-120 s, Papaverine caused no remote response w hen applied directly while adenosine and NO donors caused similar, late-ons et (10-20 s), dose-dependent, remote responses in both preparations. Remark ably however, only adenosine initiated a consistent remote arteriolar dilat ion when applied to the tissue site. Thus, increases in tissue adenosine ma y be critical for vascular communication of metabolic demands without regar d to the specific blood flow path.