Identification and Role of Serotonin 5-HT sub(1A) and 5-HT sub(1B) Receptors in Primary Cultures of Rat Embryonic Rostral Raphe Nucleus Neurons

• Published in: Journal of neurochemistry Vol. 72; no. 5; pp. 1791 - 1801
• Main Authors: Hery, F, Boulenguez, P, Semont, A, Hery, M, Pesce, G, Becquet, D, Faudon, M, Deprez, P, Fache, M-P
• Format: Journal Article
• Language: English
• Published: 01-05-1999
• ISSN: 0022-3042
• DOI: 10.1046/j.1471-4159.1999.0721791.x

Autoregulatory mechanisms affecting serotonin [5-hydroxytryptamine (5-HT)] release and synthesis during the early period of development were investigated in dissociated cell cultures raised from embryonic rostral rat rhombencephalon. The presence of 5-HT sub(1A) and 5-HT sub(1B) receptors in serotoninergic neurons was assessed using binding assays. The involvement of 5-HT sub(1A) and 5-HT sub(1B) receptors in the control of the synthesis and release of [ super(3)H]5-HT was studied using biochemical approaches with several serotoninergic receptor ligands. A mean decrease of 30% in [ super(3)H]5-HT synthesis and release was observed in the presence of 5-HT (10 super(-8) M), the 5-HT sub(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), the 5HT sub(1B/1A) agonist 5-methoxy-3-(1,2,5,6-tetrahydro-4-pyridinyl)-1H-indole (RU 24969), the 5-HT sub(1B) agonist 3-(1,2,5,6-tetrahydropyrid-4-yl) pyrrolo [3,2-b]pyrid-5-one (CP-93, 129), and the 5-HT sub(1D/1B) agonist sumatriptan. Inhibition of 5-HT synthesis and release induced by 8-OH-DPAT was blocked by chiral N-tert-butyl-3- [1-[1-(2-methoxy)phenyl]piperazinyl]-1-phenylpropionamide dihydrochloride quaternary-hydrate (WAY 100135) (10 super(-7) M) or methyl 4-[4-[4-(1,1,3-trioxo-2H-1,2-benzoisothiazol-2-yl)butyl]-1-piperaz inyl] -1H-indole-2-carboxylate (SDZ 216-525) (10 super(-7) M), and that of CP-93, 129 was blocked by methiothepin (10 super(-7) M). Paradoxically, extracellular levels of [ super(3)H]5-HT increased in the presence of 8-OH-DPAT and RU 24969 at 10 super(-6) M. 5-HT uptake experiments showed that these two agonists interacted with the 5-HT transporter. 5-HT sub(1) binding sites (620 fmol/mg of protein) and 5-HT sub(1A) (482 fmol/mg of protein) and 5-HT sub(1B) (127 fmol/mg of protein) receptors were detected in 12-day in vitro cell cultures. Experiments carried out with tetrodotoxin suggested that 5-HT sub(1A) receptors are located on nerve cell bodies, whereas 5-HT sub(1B) receptors are located on the nerve terminals. We concluded that autoregulatory mechanisms involving 5-HT sub(1A) and 5-HT sub(1B) autoreceptors are functionally mature in cells from rostral raphe nuclei during the early period of development.