Abstract
Prolactin secretion is controlled by the hypothalamus through different neurotransmitters which interact with multiple receptor subtypes. The discovery of different families of receptors for serotonin (5-HT1-5-HT7) and excitatory aminoacids (NMDA,KA,AMPA and metabotropic receptors) ilustrates the complexity of this regulation. Moreover, in the rat the role of different neurotransmitters changes during pubertal development. Present experiments were carried out to analyse the interactions between AMPA and serotoninergic receptors in the control of prolactin secretion in prepubertal male rats. For this purpose, 16 and 23-day old male rats were treated with 5-hydroxytryptophan (5-HTP, precursor of serotonin synthesis) plus fluoxetine (blocker of serotonin reuptake), 8-OH-DPAT (agonist of 5-HT1A receptors), DOI and α-Me-5-HT (agonists of 5-HT2 receptors), 1-phenylbiguanide (agonist of 5-HT3 receptors) alone or in combination with AMPA (agonist of AMPA receptors). The results obtained indicate that: (a) activation of 5-HT1A receptors stimulated PRL secretion on day 16 and inhibited it on day 23; activation of 5-HT2 receptors stimulated PRL secretion on days 16 and 23, whereas activation of 5-HT3 receptors inhibited PRL release only on day 23; (b) activation of AMPA receptors inhibited PRL secretion on day 23, but not on day 16 and (c) a cross-talk is apparent between 5-HT2 and AMPA receptors in the regulation of PRL secretion, the stimulatory effect of DOI being blocked by AMPA.
Resumen
La secreción de prolactina se controla por el hipotálamo a través de diferentes neurotransmisores que interactúan con múltiples subtipos de receptores. El descubrimiento de diferentes receptores para serotonina agrupados en siete familias y aminoácidos excitatorios (NMDA, KA, AMPA y receptores metabotrópicos) ilustran la complejidad de esta regulación. Además, el papel de los diferentes neurotransmisores cambia en la rata durante el desarrollo puberal. Los experimentos se llevan a cabo para analizar las interacciones entre los receptores AMPA y los receptores serotoninérgicos en el control de la secreción de prolactina en ratas macho prepúberes. Para ello, machos de 16 y de 23 días de edad se tratan con 5-hidroxitriptófano (5-HTP, precursor de la síntesis de serotonina) más fluoxetina (bloqueante de la recaptación de serotonina), 8-OH-DPAT (agonista de los receptores 5-HT1A), DOI y α-Me-5-HT (agonistas de los receptores 5-HT2) 1-fenilbiguanida (agonista de los receptores 5-HT3) solos o en combinación con AMPA (agonista de los receptores AMPA). Los resultados obtenidos indican que: (a) la activación de los receptores 5-HT1A estimula la secreción de PRL el día 16 y la inhibe el día 23; la activación de los receptores 5-HT2 estimula la secreción de PRL el día 16 y 23, mientras que la activación de los receptores 5-HT3 inhibe la secreción de PRL sólo el día 23; (b) la activación de los receptores AMPA inhibe la secreción de PRL el día 23, pero no el día 16; y (c) hay una interrelación aparente entre los receptores 5-HT2 y los receptores AMPA en el control de la regulación de la secreción de PRL, como lo demuestra el hecho de que el efecto estimulador del DOI es bloqueado por AMPA.
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Pinilla, L., González, L.C., Tena-Sempere, M. et al. Interactions between serotoninergic and aminoacidergic pathways in the control of PRL secretion in prepubertal male rats. J. Physiol. Biochem. 57, 237–244 (2001). https://doi.org/10.1007/BF03179817
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DOI: https://doi.org/10.1007/BF03179817