Presynaptic opioid delta‐receptors in the rabbit mesenteric artery.
- 1 October 1986
- journal article
- research article
- Published by Wiley in The Journal of Physiology
- Vol. 379 (1) , 217-228
- https://doi.org/10.1113/jphysiol.1986.sp016249
Abstract
1. Excitatory junction potentials (e.j.p.s) evoked by nerve stimulation were recorded from muscle cells of the rabbit isolated mesenteric artery. At 0.03 Hz the e.j.p. amplitudes were stable. When a train of fifteen pulses was applied at 0.25 Hz or at higher frequencies (0.5, 1 and 2 Hz), e.j.p.s showed an initial facilitation followed by depression. 2. [Met5]enkephalin 0.1 and 1 .mu.mol/l, [D-Ala2, D-Leu5]enkephalin 0.1 and 1, but not 0.01 .mu.mol/l, and [D-Pen2, L-Pen5]enkephalin 3 .mu.mol/l all depressed the e.j.p.s evoked by trains of fifteen pulses at 1 Hz. When more than one concentration was used ([Met5]enkephalin, [D-Ala2, D-Leu5]enkephalin), the inhibition was concentration dependent. It was always greater for the first few e.j.p.s than for the later ones in a train. [Met5]enkephalin 1 .mu.mol/l reduced the first e.j.p. at 1 Hz and the e.j.p.s evoked by 0.03 Hz to a similar extent. 3. The inhibitory effect of [Met5]enkephalin 1 .mu.mol/l on e.j.p.s persisted in the presence of yohimbine 0.3 .mu.mol/l. Naloxone 1 .mu.mol/l did not interfere with the effect of [Met5]enkephalin 1 .mu.mol/l. Naloxone 10 .mu.mol/l depressed some e.j.p.s and prevented the inhibition by [Met5]enkephalin 1 .mu.mol/l. Neither ICI 154129 10 .mu.mol/l nor ICI 174864 0.3 .mu.mol/l had any effect of their own and both compounds antagonized the action of [Met5]enkephalin 1 .mu.mol/l. 4. Normorphine 10 .mu.mol/l, fentanyl 1 .mu.mol/l, ethylketocyclazocine 0.1 .mu.mol/l, and dynorphin A(1-13) 1 .mu.mol/l were all ineffective. Ethylketocyclazocine 1 .mu.mol/l did not change the e.j.p.s either, but antagonized [Met5]enkephalin 1 .mu.mol/l. 5. [Met5]enkephalin 1 .mu.mol/l failed to influence both the resting membrane potential of the muscle cells and the depolarizing effect of noradrenaline 3 and 30 .mu.mol/l. 6. We suggest that the axon terminals of post-ganglionic sympathetic neurones in the rabbit mesenteric artery possess opioid .delta.-, but not .mu.- or .kappa.-receptors. The activation of presynaptic .delta.-receptors inhibits the release of the neuroeffector transmitter. There is no evidence for any effect of co-released endogenous opioid peptides under our experimental conditions.This publication has 33 references indexed in Scilit:
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