[Absence of the effect of opioid peptides on muscarine receptors in the frog vestibular apparatus].
We studied the effects of opioid peptide leu-enkephaline, a specific antagonist of acetylcholine receptors atropine, and non-selective opiate antagonist naloxone on synaptic transmission and responses evoked by acetylcholine in semicircular organs of the frog. A decrease in frequency of acetylcholine (0.1-5.0 microM) responses under leu-enkephaline (10 nM) id not differ from the frequency decline induced by leu-enkephaline alone. Atropine (1 microM) left the response to leu-enkephaline intact while blocking the excitatory effect of acetylcholine. No modification of the acetylcholine response under leu-enkephaline was observed in the presence of naloxone (1 microM). The findings suggest that no interaction exists between the acetylcholine-mediated excitatory action on resting activity in the isolated semicircular canal preparation and the suppressive action of leu-enkephaline.
Andrianov
Iu N
IuN
I. P. Pavlov Institute of Physiology, Russian Acad. Sci., 199034, St. Petersburg, Nab. Makarova, 6, Russia.
Ryzhova
I V
IV
Tobias
T B
TB
D000109:Acetylcholine / Q000494:pharmacology*; D000344:Afferent Pathways / Q000187:drug effects; D000818:Animals; D004347:Drug Interactions; D004743:Enkephalin, Leucine / Q000494:pharmacology*; D066298:In Vitro Techniques; D011896:Rana temporaria; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012665:Semicircular Canals / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects; D014722:Vestibule, Labyrinth / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*
D011976:Receptors, Muscarinic; D004743:Enkephalin, Leucine; D000109:Acetylcholine