Regional differences of the effect of σ receptor ligands on the acetylcholine release in the rat brain
The effects of (±)N-allyl-normetazocine on the release of acetylcholine from different areas of guinea-pig and rat brain were investigated. 1. The drug did not modify the electrically (2 Hz) evoked tritium efflux from guinea-pig cerebral cortex, thalamus and caudate nucleus slices, preloaded with 3H-choline 0.1 μmol/l and superfused with Krebs solution containing hemicholinium-3 10 μmol/l. 2. (±)N-allyl-normetazocine 10 μmol/l. enhanced the evoked 3H efflux from guinea-pig brain slices superfused with Krebs solution containing physostigmine 30 μmol/l or oxotremorine 0.3 -1 gmol/l; the effect was naloxone-insensitive and was abolished by atropine 0.15 μmol/l, but not by pirenzepine 1 μmol/l. 3. (±)N-allyl-normetazocine 5 μmol/l enhanced the electrically evoked release of endogenous acetylcholine as well, in a naloxone-insensitive way. 4. Both (±) and (+)N-allyl-normetazocine were without effect on 3H efflux from rat caudate nucleus slices electrically stimulated at 0.2 Hz frequency, after preloading with 3H-choline and during superfusion with hemicholinium-3. 5. The results are discussed in view of the antimuscarinic properties of the drug.