Enkephalin and alpha-adrenergic receptors: evidence for both common and differentiable regulatory pathways and down-regulation of the enkephalin receptor.
Several clones of neuroblastoma-glioma NG108-15 hybrid cells were used to reveal whether the regulation of opiate receptor density interacts with the regulation of alpha-adrenergic or acetyl-choline receptors. Low density of alpha-adrenergic receptors in 3 selected clones was accompanied with similar reduction in the density of enkephalin receptors but not in muscarinic acetyl-choline receptors. Yet opiate antagonists that increased the number of opiate receptors in the parent NG108-15 cells in a stereospecific manner had no similar effect on the number of alpha-adrenergic receptors. Moreover, the stable enkephalin analogue D-ala-2-methionine enkephalinamide, but not the opiate alkaloid morphine, decreased the binding of 3H-DAMEA to the membranes and induced down-regulation of enkephalin receptors. Yet DAMEA had no effect on the binding of the alpha-adrenergic antagonist 3H-yohimbine. The study suggests that alpha-adrenergic and enkephalin receptors may share some common regulatory pathways but opiate peptides and antagonists selectively decrease or increase the density of enkephalin receptors, respectively, with no effect on alpha-adrenergic receptor density.
D000818:Animals; D004723:Endorphins / Q000494:pharmacology; D006822:Hybrid Cells; D066298:In Vitro Techniques; D009294:Narcotics / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011950:Receptors, Cholinergic / Q000502:physiology; D011976:Receptors, Muscarinic / Q000502:physiology; D011957:Receptors, Opioid / Q000502:physiology*
D004723:Endorphins; D009294:Narcotics; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D011957:Receptors, Opioid