Extensive overlap of mu-opioid and nicotinic sensitivity in cortical interneurons

Abstract

We studied μ-opioid transmission in acute slices of rat neocortex using whole-cell recordings and single-cell reverse transcription-polymerase chain reaction. The μ-opioid receptor (MOR) was found in γ-aminobutyric acidergic (GABAergic) interneurons that were either layer I cells frequently expressing neuropeptide Y or layers II-V cells expressing vasoactive intestinal peptide and enkephalin (Enk). We found that μ-opioid agonists inhibit these interneurons that are selectively excited by nicotinic agonists. The extensive overlap of μ-opioid and nicotinic responsiveness allowed μ-opioid agonists to inhibit nicotinic excitation of responsive interneurons and of their GABAergic output onto pyra..