Photoelectric measurement of neurogenic vasoconstriction in jejunal branches of the rabbit mesenteric artery reveals the presence of presynaptic opioid delta-receptors.
The perivascular nerves of rabbit mesenteric arteries were stimulated with 15 pulses at 2 Hz, and decreases in external diameter were measured by means of a photoelectric device. Both extra- and intraluminally added [Met5]enkephalin 1 mumol/l depressed vasoconstriction, although with the second mode of application a larger inhibition occurred. Therefore, in the subsequent experiments all opioids were added into the lumen. [Met5]enkephalin 0.1 mumol/l had no effect. [D-Pen2, L-Pen5]enkephalin 3 mumol/l was less potent than [Met5]enkephalin 1 mumol/l. ICI 174864 1 mumol/l was also without effect when given alone, but antagonized the action of [Met5]enkephalin 1 mumol/l. Ethylketocyclazocine, dynorphin A(1-13), normorphine and DAGO, all 1 mumol/l, were ineffective. [Met5]enkephalin 1 mumol/l did not change the vasoconstriction evoked by the application of noradrenaline (0.1-3 mumol/l). It is concluded that in the mesenteric artery action potential-induced transmitter release, and in consequence vasoconstriction can be inhibited by the activation of presynaptic opioid delta-receptors.
Illes
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Ramme
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Busse
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R
D000818:Animals; D004558:Electric Stimulation; D004723:Endorphins / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007583:Jejunum / Q000098:blood supply; D008297:Male; D008638:Mesenteric Arteries / Q000294:innervation*; D009638:Norepinephrine / Q000494:pharmacology; D011817:Rabbits; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D017465:Receptors, Opioid, delta; D013569:Synapses; D014661:Vasoconstriction / Q000187:drug effects
D004723:Endorphins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D009638:Norepinephrine