Muscarinic modulation of acetylcholine release from slices of guinea pig nucleus basalis magnocellularis.
Spontaneous and electrically evoked endogenous acetylcholine release and [3H]-choline efflux from slices of guinea pig nucleus basalis magnocellularis (nbM) were studied. Tetrodotoxin reduced the spontaneous endogenous release by 55%, while the Ca(2+)-free medium reduced it by about 30%. Evoked [3H]-choline efflux was Na+ and Ca2+ dependent and frequency related. Physostigmine, 30 microM, nearly halved the stimulation-evoked efflux; atropine, 0.15 microM, not only antagonized, but even reversed this effect into facilitation. Pirenzepine, 1 microM, and AFDX 116, 1 microM, were less effective than atropine, and reversed the inhibitory effect of physostigmine only when applied together. 4-DAMP, 0.01 microM, was ineffective. These findings indicate that acetylcholine release in guinea pig nbM slices is inhibited by the cooperation of muscarinic autoreceptors, possibly belonging to the M1 and M2 subclasses.
Siniscalchi
A
A
Institute of Pharmacology, University of Ferrara, Italy.
Badini
I
I
Cintra
A
A
Fuxe
K
K
Bianchi
C
C
Beani
L
L
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002794:Choline / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D010890:Pirenzepine / Q000031:analogs & derivatives / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000502:physiology*; D013377:Substantia Innominata / Q000187:drug effects / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D010276:Parasympatholytics; D010880:Piperidines; D011976:Receptors, Muscarinic; D010890:Pirenzepine; D013779:Tetrodotoxin; D001285:Atropine; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D010830:Physostigmine; D002794:Choline; D000109:Acetylcholine; C048593:otenzepad; D002118:Calcium