Cholinergic terminals in rat hippocampus possess 5-HT1B receptors mediating inhibition of acetylcholine release.
The effects of 5-hydroxytryptamine (5-HT) on the release of [3H]acetylcholine ([3H]ACh) from rat hippocampal nerve endings were investigated using synaptosomes labelled with [3H]choline and depolarized in superfusion with 15 mM KCl. The release of [3H]ACh was concentration dependently inhibited by exogenous 5-HT. The concentration-response curve of 5-HT was shifted to the right in a parallel way by methiothepin. The 5-HT2 antagonists ketanserin or methysergide did not antagonize the effect of 5-HT. The 5-HT1 agonist 5-methoxy-3-[1,2,3,6-tetrahydropyridin-4-yl]-1H-indole (RU 24969) mimicked 5-HT, whereas the 5-HT1A selective agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) was ineffective. When used as a 5-HT1A/5-HT1B antagonist, (-)propranolol antagonized 5-HT whereas spiperone (a 5-HT1A displacer) did not. The 5-HT1C selective antagonist mesulergine was also ineffective towards 5-HT. It can be concluded that hippocampal cholinergic terminals are endowed with inhibitory 5-HT receptors which appear to belong to the 5-HT1B subtype.
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000502:physiology
D007211:Indoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C025145:5-methoxy 3-(1,2,3,6-tetrahydro-4-pyridinyl)1H indole; D012701:Serotonin; D000109:Acetylcholine