Modulatory action of acetylcholine on cerebrovascular sympathetic neurotransmission.
1. Acetylcholine (10 micrograms/min) diminished the electrically-induced cerebral blood flow reductions. Atropine (1-2 mg) partially blocked this inhibitory effect. 2. Exogenously administered noradrenaline (1-10 micrograms) and tyramine (50-500 micrograms) reduced cerebral blood flow but this effect was unchanged by acetylcholine infusion. 3. Acetylcholine inhibited the nonadrenergic component of the electrically-induced contraction at a concentration greater than or equal to 10(-6) M and potentiated the adrenergic component at a concentration greater than or equal to 10(5) M. Atropine 10(-7) M) inhibited both of these effects. In addition, acetylcholine (10(-4) M) enhanced the electrically-evoked [3H]noradrenaline overflow. 4. These results show that: (a) acetylcholine modulates cerebrovascular sympathetic neurotransmission by acting on muscarinic receptors; and (b) the potentiating effect of acetylcholine is achieved by a mechanism involving increases in noradrenaline release.
Miranda
F J
FJ
Centro de Investigación, Hospital La Fe, Valencia, Spain.
Torregrosa
G
G
Salom
J B
JB
Alabadí
J A
JA
Alvarez
C
C
Alborch
E
E
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002536:Cerebral Arteries / Q000187:drug effects / Q000294:innervation; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004558:Electric Stimulation; D005260:Female; D006041:Goats / Q000502:physiology*; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000294:innervation; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology; D014439:Tyramine / Q000494:pharmacology
D013779:Tetrodotoxin; D000109:Acetylcholine; D009638:Norepinephrine; D014439:Tyramine