ABSTRACT
Resumen: INTRODUCCIÓN: La depresión mayor (DM) se debe a la interacción de factores ambientales, genéticos y epigenéticos, que atenúan la transmisión monoaminérgica en el cerebro. Sin embargo, poco se conoce sobre los mecanismos fisiopatológicos que subyacen a ella. OBJETIVO: Proponer una visión integral sobre la fisiopatología de la DM y los mecanismos de acción de los fármacos antidepresivos. MÉTODO: Se empleó la base PubMed para la búsqueda bibliográfica. La mayoría son investigaciones experimentales y estudios de genética molecular o de imágenes cerebrales en humanos. RESULTADOS: La DM se asocia con: i) menor volumen de la corteza cingulada anterior; ii) hiper-metabolismo del área Cg25; iii) menor expresión del receptor 5-HT1A; iv) mayor expresión de la monoamino oxidasa A. Algunos polimorfismos están asociados a la fisiopatología. El estrés crónico reduce la expresión del 5-HT1A. Los antidepresivos atenúan el hiper-metabolismo del área Cg25, estimulan la neurogénesis y activan la vía del AMPc. Encontramos que la imipramina aumenta y reduce la expresión de G α s y G α z, respectivamente (datos sin publicar). DISCUSIÓN Y CONCLUSIÓN: El déficit en la transmisión monoaminérgica puede deberse a: i) el polimorfismo G1463A en el gen de la enzima hTPH2 que reduce la síntesis de serotonina; ii) el polimorfismo C(-1019)G en el gen del receptor 5-HT1A, aumentando su transcripción en el rafé e implicando menor liberación del neurotransmisor; iii) mayor degradación de las monoaminas. La menor expresión del receptor 5-HT1A se discute considerando su acción inhibitoria en la corteza prefrontal. Los cambios en la expresión de G α s y G α z coinciden con la estimulación de la vía del AMPc.
Abstract: INTRODUCTION: The major depressive disorder (MDD) arises from the interaction of environmental, genetic and epigenetic factors, producing a deficit in monoaminergic transmission within the brain. However, our understanding of its pathophysiology is quite limited. OBJECTIVE: To reach an integrative view of the MDD pathophysiology, as well as the mechanisms of action of antidepressant drugs. METHOD: We used the PubMed database to search for the documents by using the appropriate key words. Most of them are experimental research and molecular genetics and brain imaging studies in humans. RESULTS: The pathophysiology of MDD is characterized by: i) shrinkage of the cingulate anterior cortex; ii) hyper-metabolism of the Cg25 area; iii) lower expression of the 5-HT1A receptor; iv) enhanced expression of monoamine oxidase A. Besides, certain gene polymorphisms are strongly linked to the pathophysiology, and there is evidence that 5-HT1A receptor expression is reduced by psychological stress. Antidepressants reverse the hyper-metabolic state of Cg25, stimulate neurogenesis and the cAMP pathway. We found that imipramine increases and reduces the expression of G α s and G α z, respectively (data no published). DISCUSSION AND CONCLUSION: The disruption in monoaminergic transmission could be mediated by: i) the G1463A hTPH2 polymorphism that reduces the serotonin synthesis; ii) the C(-1019)G 5-HT1A polymorphism that increases the receptor expression in the dorsal rafe, and reduces serotonin release; iii) an increase in monoamine degradation. The reduced 5-HT1A expression is discussed considering its inhibitory properties in the prefrontal cortex. The effects of imipramine on G α s and G α z are in agreement with the antidepressant-induced stimulation of the cAMP pathway.
ABSTRACT
The present work is a thorough investigation of the degree of reproductive isolation between Meccus mazzottii and Meccus longipennis, Meccus picturatus, Meccus pallidipennis and Meccus bassolsae, as well as between M. longipennis and M. picturatus. We examined fertility and segregation of morphological characteristics in two generations of hybrids derived from crosses between these species. The percentage of pairs with (fertile) offspring was highest in the set of crosses between M. longipennis and M. picturatus, and lowest between M. mazzottii and M. picturatus. Most first-generation (F1) individuals from crosses involving M. mazzottii were morphologically similar to this species, while only F1 x F1 progeny of parental crosses between M. mazzottii and M. longipennis had offspring second generation that looked like M. mazzottii. The results indicate that different degrees of reproductive isolation apparently exist among the species of the Phyllosoma complex examined in this study. The biological evidence obtained in this study does not support the proposal that M. longipennis and M. picturatus are full species. It could indicate on the contrary, that both could be considered as subspecies of a single polytypic species. On the other hand, biological evidence supports the proposal that M. mazzottii is a full species.