Interaction between prejunctional α2‐receptors and neuronal transmitter reuptake in small mesenteric arteries from the rat

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Abstract
The role of the prejunctional α2‐receptors for the response to vaso‐constrictor nerve stimulation has been examined before and after inhibition of neuronal transmitter reuptake in mesenteric resistance vessels from the rat. Small arteries (diameter about 200 μm) feeding the jejunum were mounted in a myograph for recording of their isometric wall tension during transmural field stimulation of the intramural nerves. Blockade of prejunctional α2‐receptors with 0.01 μm idazoxan (RX 781094) caused a marginal potentiation of the neurogenic response when neuronal reuptake was left intact. Also, inhibition of reuptake alone with 3 μm cocaine had little effect on the response. However, when both α2‐receptors and reuptake had been inhibited, a strong enhancement of the neurogenic vasoconstriction was observed. Similar findings were made when yohimbine and LU 3–010 instead were used for α2‐blockade and reuptake inhibition, respectively. The results thus indicate that in these resistance arteries the effector response is normally influenced by the combined activity of α2‐receptors and uptake, and that failure of one mechanism increases the activity of the other, so as to maintain a largely constant effector response.

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