In vivo evidence for acetylcholine control of serotonin release in the cat caudate nucleus: influence of halothane anaesthesia.
Using a push-pull cannula technique and an isotopic method for the estimation of [3H]serotonin continuously synthesized from [3H]tryptophan, the effects of acetylcholine were investigated on the in vivo release of [3H]serotonin in the cat basal ganglia and the dorsal raphe nucleus. The unilateral striatal application of acetylcholine (5 x 10(-5) M) reduced local release of [3H]serotonin. This effect was mimicked by nicotine (5 x 10(-5) M) and prevented by mecamylamine (10(-6) M. Oxotremorine (5 x 10(-5) M) had no effect on the local release of [3H]serotonin. All these treatments failed to modify [3H]serotonin release in the ipsilateral substantia nigra or in the dorsal raphe nucleus. The superfusion of serotonergic nerve terminals of the caudate nucleus with tetrodotoxin prevented the inhibitory acetylcholine-induced effect on serotonin release. Furthermore, bicuculline (5 x 10(-5) M) in the caudate nucleus blocked the effect of nicotine, while gamma-aminobutyric acid (10(-5) M) induced a decrease in local release of [3H]serotonin. These data strongly suggest that the inhibitory control exerted by acetylcholine on serotonergic transmission could involve gamma-aminobutyric acid interneurons. Acetylcholine-induced changes in [3H]serotonin release were only observed in non-anaesthetized "encéphale isolé" cats and not in halothane-anaesthetized animals. The possibility that such a regulation could be presynaptic (direct or through other neurotransmitters) or related to a change in the activity of the serotonergic raphe-striatal neuronal system is discussed.
Becquet
D
D
INSERM-U6, Marseille, France.
Faudon
M
M
Hery
F
F
D000109:Acetylcholine / Q000502:physiology*; D000758:Anesthesia; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002415:Cats; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism*; D003655:Decerebrate State; D005260:Female; D006221:Halothane / Q000008:administration & dosage*; D008297:Male; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D012701:Serotonin; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D000109:Acetylcholine; D006221:Halothane; D001640:Bicuculline