Modulation of (3)H-noradrenaline release by presynaptic opioid, cannabinoid and bradykinin receptors and beta-adrenoceptors in mouse tissues

Abstract

Release-modulating opioid and cannabinoid (CB) receptors, beta-adrenoceptors and bradykinin receptors at noradrenergic axons were studied in mouse tissues (occipito-parietal cortex, heart atria, vas deferens and spleen) preincubated with (3)H-noradrenaline. Experiments using the OP(1) receptor-selective agonists DPDPE and DSLET, the OP(2)-selective agonists U50488H and U69593, the OP(3)-selective agonist DAMGO, the ORL(1) receptor-selective agonist nociceptin, and a number of selective antagonists showed that the noradrenergic axons innervating the occipito-parietal cortex possess release-inhibiting OP(3) and ORL(1) receptors, those innervating atria OP(1), ORL(1) and possibly OP(3) receptors, and those innervating the vas deferens all four opioid receptor types. Experiments using the non-selective CB agonists WIN 55,212-2 and CP 55,940 and the CB(1)-selective antagonist SR 141716A indicated that the noradrenergic axons of the vas deferens possess release-inhibiting CB(1) receptors. Presynaptic CB receptors were not found in the occipito-parietal cortex, in atria or in the spleen. Experiments using the non-selective beta-adrenoceptor agonist isoprenaline and the beta(2)-selective agonist salbutamol, as well as subtype-selective antagonists, demonstrated the occurrence of release-enhancing beta(2)-adrenoceptors at the sympathetic axons of atria and the spleen, but demonstrated their absence in the occipito-parietal cortex and the vas deferens. Experiments with bradykinin and the B(2)-selective antagonist Hoe 140 showed the operation of release-enhancing B(2) receptors at the sympathetic axons of atria, the vas deferens and the spleen, but showed their absence in the occipito-parietal cortex. The experiments document a number of new presynaptic receptor locations. They confirm and extend the existence of marked tissue and species differences in presynaptic receptors at noradrenergic neurons.

Figure 1

Effects of the opioid receptor agonists DPDPE, DSLET, U50488H and DAMGO on the evoked overflow of tritium from mouse occipito-parietal cortex slices (A), and interaction of DAMGO with antagonists (B). S₁ to S₆ each consisted of a single pulse. Agonists were added at increasing concentrations before S₂–S₆. Agonists were given either alone or (DAMGO) with the antagonists indicated, which were present throughout superfusion. Ordinates, evoked overflow of tritium, calculated from S_n/S₁ ratios and expressed as a percentage of control. Values are means±s.e.mean from 6–22 brain slices.

Figure 2

Effect of the ORL₁ receptor agonist nociceptin on the evoked overflow of tritium from mouse occipito-parietal cortex slices (A) and pieces of mouse atria (B) and vas deferens (C), and interaction with the antagonist PheΨ. S₁ to S₆ each consisted of either a single pulse (occipito-parietal cortex) or 20 pulses at 50 Hz (atria and vas deferens). Nociceptin was added at increasing concentrations before S₂–S₆. Nociceptin was given either alone or with PheΨ, which was present throughout superfusion. Naloxone (1 μM) was present throughout superfusion in all experiments. Ordinates, evoked overflow of tritium, calculated from S_n/S₁ ratios and expressed as a percentage of control. Values are means±s.e.mean from 5–8 tissue pieces.

Figure 3

Effects of the opioid receptor agonists DPDPE, DSLET, U50488H, U69593 and DAMGO on the evoked overflow of tritium from pieces of mouse atria (A) and vas deferens (B). S₁ to S₆ each consisted of 20 pulses at 50 Hz. Agonists were added at increasing concentrations before S₂–S₆. Ordinates, evoked overflow of tritium, calculated from S_n/S₁ ratios and expressed as a percentage of control. Values are means±s.e.mean from 5–22 tissue pieces.

Figure 4

Effect of the CB receptor agonist WIN 55,212-2 on the evoked overflow of tritium from pieces of mouse vas deferens, and interaction with the antagonist SR 141716A. S₁ to S₆ each consisted of 20 pulses at 50 Hz. WIN 55,212-2 was added at increasing concentrations before S₂–S₆. WIN 55,212-2 was given either alone or with SR 141716A, which was present throughout superfusion. Ordinates, evoked overflow of tritium, calculated from S_n/S₁ ratios and expressed as a percentage of control. Values are means±s.e.mean from 6–10 tissue pieces.

Figure 5

Effect of the β-adrenoceptor agonist salbutamol on the evoked. overflow of tritium from pieces of mouse atria (A) and spleen (B), and interaction with the antagonists CGP 20712A or ICI 118,551. S₁ to S₆ each consisted of either 20 pulses at 50 Hz (atria) or 120 pulses at 3 Hz (spleen). Salbutamol was added at increasing concentrations before S₂–S₆. Salbutamol was given either alone or with CGP 20712A or ICI 118,551, which were present throughout superfusion. Phentolamine (1 μM) was present throughout superfusion in all experiments. Ordinates, evoked overflow of tritium, calculated from S_n/S₁ ratios and expressed as a percentage of control. Values are means±s.e.mean from 4–14 tissue pieces.

Figure 6

Effect of bradykinin on the evoked overflow of tritium from pieces of mouse atria (A), vas deferens (B) and spleen (C), and interaction with the antagonist Hoe 140. S₁ to S₆ each consisted of 120 pulses at 3 Hz. Bradykinin was added at increasing concentrations before S₂–S₆. Bradykinin was given either alone or with Hoe 140, which was present throughout superfusion. Ordinates, evoked overflow of tritium, calculated from S_n/S₁ ratios and expressed as a percentage of control. Values are means±s.e.mean from 5–33 tissue pieces.