Serotonergic fibers distribution in the midline and intralaminar thalamic nuclei in the rock cavy ( Kerodon rupestris )

• Published in: Brain research 2014-10, Vol.1586, p.99-108
• Main Authors: de Medeiros Silva, Alane, de Santana, Melquisedec Abiaré Dantas, de Góis Morais, Paulo Leonardo Araújo, de Sousa, Twyla Barros, Januário Engelberth, Rovena Clara Galvão, de Souza Lucena, Eudes Euler, Campêlo, Clarissa Loureiro das Chagas, Sousa Cavalcante, Jeferson, Cavalcante, Judney Cley, de Oliveira Costa, Miriam Stela Maris, Nascimento, Expedito Silva do
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Biological and medical sciences; Fiber morphology; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Intralaminar Thalamic Nuclei - anatomy & histology; Midline Thalamic Nuclei - anatomy & histology; Midline/intralaminar nuclei; Nerve Fibers - metabolism; Neurology; Optical density; Rock cavy; Serotonergic system; Serotonin - metabolism; Thalamus; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2014.08.047

Abstract The thalamic midline/intralaminar complex is part of the higher-order thalamus, which receives little sensory input, and instead forms extensive cortico-thalamo-cortical pathways. The midline thalamic nuclei connect with the medial prefrontal cortex and the medial temporal lobe. On the other hand, the intralaminar nuclei connect with the fronto-parietal cortex. Taking into account this connectivity pattern, it is not surprising that the midline/intralaminar complex has been implicated in a broad variety of cognitive functions, including memory process, attention and orientation, and also reward-based behavior. Serotonin (5-HT) is a neurotransmitter that exerts different post-synaptic roles. Serotonergic neurons are almost entirely restricted to the raphe nuclei and the 5-HT fibers are distributed widely throughout the brain, including the midline/intralaminar complex. The present study comprises a detailed description of the morphologic features and semiquantitative analysis of 5-HT fibers distribution in the midline/intralaminar complex in the rock cavy, a typical rodent of the Northeast region of Brazil, which has been used by our group as an anatomical model to expand the comprehension about phylogeny on the nervous system. The 5-HT fibers in the midline/intralaminar nuclei of the rock cavy were classified into three distinct categories: (1) beaded fibers, which are relatively fine and endowed with large varicosities; (2) fine fibers, with thin axons and small varicosities uniformly distributed in whole axon; and (3) stem axons, showing thick non-varicose axons. Moreover, the density of 5-HT fibers is variable among the analyzed nuclei. On the basis of this diversity of the morphological fibers and the differential profile of optical density among the midline/intralaminar nuclei of the rock cavy, we conclude that the serotonergic system uses a diverse morphologic apparatus to exert a large functional repertory in the midline/intralaminar thalamic nuclei.