Central noradrenergic neurons: a locus for the functional interplay between alpha-2 adrenoceptors and opiate receptors.
The locus coeruleus (LC) contains the largest clusters of noradrenergic neurons in the brain. Single-cell recordings in rats show that LC neurons can be inhibited by clonidine acting via alpha-2 adrenoceptors; morphine and opiate peptides are also inhibitory but act via separate opiate receptors. During states of opiate withdrawal LC neurons become hyperactive; under these conditions clonidine can normalize activity via alpha-2 adrenoceptors even when opiate receptors are blocked. These single-cell studies provide a possible mechanism for the clinical efficacy of clonidine in relieving the signs and symptoms of opiate withdrawal in human addicts.
D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D003712:Dendrites / Q000502:physiology; D005071:Evoked Potentials / Q000187:drug effects; D006801:Humans; D008125:Locus Coeruleus / Q000502:physiology*; D009020:Morphine / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology*; D010883:Piperoxan / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects
D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011957:Receptors, Opioid; D009020:Morphine; D010883:Piperoxan; D003000:Clonidine; D009638:Norepinephrine