Mutual interaction between presynaptic alpha sub(2)-adrenoceptors and opiod Kappa -receptors at the noradrenergic axons of rabbit brain cortex

The interaction between presynaptic, release-inhibiting alpha sub(2)-adrenoceptors and opioid receptors was studied in slices of the parieto-occipital cortex of rabbits. Clonidine and ethylketocyclazocine (EK) depressed, whereas yohimbine increased the electrically evoked overflow of tritium. It is concluded that there is an interaction between presynaptic alpha sub(2)-adrenoceptors and opioid Kappa -receptors, either at the level of the receptor themselves or of the post-receptor reaction chains. Activation of one kind of receptor blunts the inhibition of release produced by activation of the other kind of receptor.