title: Prenatal activation of 5-HT2A receptor induces expression of 5-HT1B receptor in phrenic motoneurons and alters the organization of their premotor network in newborn mice.
abstract: In newborn mice of the control [C3H/HeJ (C3H)] and monoamine oxidase A-deficient (Tg8) strains, in which levels of endogenous serotonin (5-HT) were drastically increased, we investigated how 5-HT system dysregulation affected the maturation of phrenic motoneurons (PhMns), which innervate the diaphragm. First, using immunocytochemistry and confocal microscopy, we observed a 5-HT(2A) receptor (5-HT(2A)-R) expression in PhMns of both C3H and Tg8 neonates at the somatic and dendritic levels, whereas 5-HT(1B) receptor (5-HT(1B)-R) expression was observed only in Tg8 PhMns at the somatic level. We investigated the interactions between 5-HT(2A)-R and 5-HT(1B)-R during maturation by treating pregnant C3H mice with a 5-HT(2A)-R agonist (2,5-dimethoxy-4-iodoamphetamine hydrochloride). This pharmacological overactivation of 5-HT(2A)-R induced a somatic expression of 5-HT(1B)-R in PhMns of their progeny. Conversely, treatment of pregnant Tg8 mice with a 5-HT(2A)-R antagonist (ketanserin) decreased the 5-HT(1B)-R density in PhMns of their progeny. Second, using retrograde transneuronal tracing with rabies virus injected into the diaphragm of Tg8 and C3H neonates, we studied the organization of the premotor network driving PhMns. The interneuronal network monosynaptically connected to PhMns was much more extensive in Tg8 than in C3H neonates. However, treatment of pregnant C3H mice with 2,5-dimethoxy-4-iodoamphetamine hydrochloride switched the premotoneuronal network of their progeny from a C3H- to a Tg8-like pattern. These results show that a prenatal 5-HT excess affects, via the overactivation of 5-HT(2A)-R, the expression of 5-HT(1B)-R in PhMns and the organization of their premotor network.
authors.affiliation: Laboratoire Plasticité et Physio-Pathologie de la Motricité, UMR 6196 CNRS, Université de la Méditerranée, Marseille, France. bras@dpm.cnrs-mrs.fr
authors.forename: Hélène
authors.initials: H
authors.lastname: Bras
authors.forename: Susana P
authors.initials: SP
authors.lastname: Gaytán
authors.forename: Paule
authors.initials: P
authors.lastname: Portalier
authors.forename: Sébastien
authors.initials: S
authors.lastname: Zanella
authors.forename: Rosario
authors.initials: R
authors.lastname: Pásaro
authors.forename: Patrice
authors.initials: P
authors.lastname: Coulon
authors.forename: Gérard
authors.initials: G
authors.lastname: Hilaire
mesh_terms: D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn / Q000033:anatomy & histology / Q000378:metabolism; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D005260:Female; D007650:Ketanserin / Q000494:pharmacology; D051379:Mice; D008809:Mice, Inbred C3H; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology*; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology*; D010791:Phrenic Nerve / Q000166:cytology*; D011247:Pregnancy; D044302:Receptor, Serotonin, 5-HT1B / Q000235:genetics / Q000378:metabolism*; D044402:Receptor, Serotonin, 5-HT2A / Q000235:genetics / Q000378:metabolism*; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
chemical_list: D000662:Amphetamines; D044302:Receptor, Serotonin, 5-HT1B; D044402:Receptor, Serotonin, 5-HT2A; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D007650:Ketanserin; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine