A 5-HT1A-like receptor is involved in the regulation of the embryonic rotation of Lymnaea stagnalis L.
Cilia driven rotation of the pond snail Lymnaea stagnalis embryos is regulated by serotonin (5-HT). In the present study, physiological and biochemical assays were used to identify the 5-HT receptor type involved in rotation. The 5-HTergic agonists applied stimulated the rotation by 180-400% and their rank order potency was as follows: LSD>5-HT>8-OH-DPAT>WB4101>>5-CT. The applied antagonists, spiperone, propranalol and mianserin inhibited the 5-HT or 8-OH-DPAT stimulated rotation of the embryos by 50-70%. (3)H-5-HT was bound specifically to the washed pellet of the embryo homogenates. The specific binding of (3)H-5-HT was saturable and showed a single, high affinity binding site with K(d) 7.36 nM and B(max) 221 fmol/mg pellet values. This is the first report demonstrating the high affinity binding of (3)H-5-HT to the native receptor in molluscs. All of the pharmacons that stimulated the rotation or inhibited the 5-HT or 8-OH-DPAT evoked stimulation displaced effectively the binding of (3)H-5-HT. 5-HT resulted in the inhibition of forskolin stimulated cAMP accumulation, showing that 5-HT is negatively coupled to adenylate cyclase. Our results suggest that in the 5-HTergic regulation of the embryonic rotation in L. stagnalis a 5-HT(1A)-like receptor of the vertebrate type is involved.
Hiripi
László
L
Department of Experimental Zoology, Balaton Limnological Research Institute, Hungarian Academy of Sciences, H-8237 Tihany, P.O.B. 35, Hungary. hiripi@tres.blki.hu
Elekes
Károly
K
D000818:Animals; D019521:Body Patterning / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism; D008195:Lymnaea / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D044282:Receptor, Serotonin, 5-HT1A / Q000502:physiology*; D012399:Rotation; D012701:Serotonin / Q000633:toxicity; D017366:Serotonin Receptor Agonists / Q000633:toxicity
D017366:Serotonin Receptor Agonists; D044282:Receptor, Serotonin, 5-HT1A; D012701:Serotonin